UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

þ Quarterly report pursuant to section 13 or 15(d) of the Securities Exchange Act of 1934

For the quarterly period ended September 30, 2005

OR

o Transition report pursuant to section 13 or 15(d) of the Securities Exchange Act of 1934

For the transition period from                      to                     

COMMISSION FILE NUMBER 000-49733

First Interstate BancSystem, Inc.

(Exact name of registrant as specified in its charter)

Montana	81-0331430
(State or other jurisdiction of incorporation or organization)	(IRS Employer Identification No.)

401 North 31st Street, Billings, MT	59116-0918
(Address of principal executive offices)	(Zip Code)

Registrant’s telephone number, including area code: 406/255-5390

(Former name, former address and former fiscal year, if changed since last report)

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes þ No o

Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Exchange Act). Yes o No þ

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes o No þ

The Registrant had 8,097,490 shares of common stock outstanding on September 30, 2005.

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

Quarterly Report on Form 10-Q

Index		Page
Part I. Financial Information
Item 1 —	Financial Statements (unaudited)
	Consolidated Balance Sheets September 30, 2005 and December 31, 2004		3
	Consolidated Statements of Income Three and nine months ended September 30, 2005 and 2004		4
	Consolidated Statements of Stockholders’ Equity and Comprehensive Income Nine months ended September 30, 2005 and 2004		5
	Consolidated Statements of Cash Flows Nine months ended September 30, 2005 and 2004		6
	Notes to Unaudited Consolidated Financial Statements		7
Item 2 —	Management’s Discussion and Analysis of Financial Condition And Results of Operations		12
Item 3 —	Quantitative and Qualitative Disclosures about Market Risk		22
Item 4 —	Controls and Procedures		22
Part II. Other Information
Item 1 —	Legal Proceedings		23
Item 2 —	Unregistered Sales of Equity Securities and Use of Proceeds		23
Item 3 —	Defaults Upon Senior Securities		23
Item 4 —	Submission of Matters to a Vote of Security Holders		23
Item 5 —	Other Information		23
Item 6 —	Exhibits		24
Signatures			26
Certification Pursuant to Section 302 - CEO
Certification Pursuant to Section 302 - CFO
Certification Pursuant to Section 906

2

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

Consolidated Balance Sheets

(Dollars in thousands, except share data)

(Unaudited)

	September 30,			December 31,
	2005			2004
Assets
Cash and due from banks	$	203,983		$	235,251
Federal funds sold		105,150			37,590
Interest bearing deposits in banks		14,874			83,067
Investment securities:
Available-for-sale		783,056			766,669
Held-to-maturity (estimated fair values of $106,642 as of September 30, 2005 and $103,754 as of December 31, 2004)		104,856			100,646
Total investment securities		887,912			867,315
Loans		2,982,325			2,739,509
Less allowance for loan losses		43,213			42,141
Net loans		2,939,112			2,697,368
Premises and equipment, net		120,086			121,928
Accrued interest receivable		26,931			20,569
Company-owned life insurance		61,975			60,645
Mortgage servicing rights, net of accumulated amortization and impairment reserve		20,558			17,624
Goodwill		37,390			37,390
Core deposit intangibles, net of accumulated amortization		1,457			2,217
Net deferred tax asset		3,162			1,911
Other assets		35,149			34,418
Total assets	$	4,457,739		$	4,217,293
Liabilities and Stockholders’ Equity
Deposits:
Noninterest bearing	$	847,030		$	756,687
Interest bearing		2,630,085			2,564,994
Total deposits		3,477,115			3,321,681
Securities sold under repurchase agreements		495,269			449,699
Accrued interest payable		11,498			9,529
Accounts payable and accrued expenses		27,001			16,899
Other borrowed funds		6,435			7,995
Long-term debt		57,017			61,926
Subordinated debenture held by subsidiary trust		41,238			41,238
Total liabilities		4,115,573			3,908,967
Stockholders’ equity:
Nonvoting noncumulative preferred stock without par value; authorized 100,000 shares; no shares issued or outstanding as of September 30, 2005 or December 31, 2004		—			—
Common stock without par value; authorized 20,000,000 shares; issued and outstanding 8,097,490 shares as of September 30, 2005 and 7,980,300 shares as of December 31, 2004		43,695			36,803
Retained earnings		304,288			275,172
Unearned compensation — restricted stock		(368	)		(425	)
Accumulated other comprehensive loss, net		(5,449	)		(3,224	)
Total stockholders’ equity		342,166			308,326
Total liabilities and stockholders’ equity	$	4,457,739		$	4,217,293

See accompanying notes to unaudited consolidated financial statements.

3

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

Consolidated Statements of Income

(Dollars in thousands, except per share data)

(Unaudited)

	For the three months						For the nine months
	ended September 30,						ended September 30,
	2005			2004			2005			2004
Interest income:
Interest and fees on loans	$	51,801		$	40,586		$	141,840		$	119,171
Interest and dividends on investment securities:
Taxable		7,693			6,221			21,616			18,991
Exempt from Federal taxes		1,098			1,031			3,286			3,063
Interest on deposits in banks		59			26			363			33
Interest on Federal funds sold		772			279			1,829			498
Total interest income		61,423			48,143			168,934			141,756
Interest expense:
Interest on deposits		12,039			8,513			31,681			25,361
Interest on Federal funds purchased		1			—			23			33
Interest on securities sold under repurchase agreements		3,380			1,018			8,401			2,143
Interest on other borrowed funds		37			6			83			37
Interest on long-term debt		640			539			1,954			1,668
Interest on subordinated debenture held by subsidiary trust		709			513			1,970			1,424
Total interest expense		16,806			10,589			44,112			30,666
Net interest income		44,617			37,554			124,822			111,090
Provision for loan losses		1,375			2,387			4,365			7,346
Net interest income after provision for loan losses		43,242			35,167			120,457			103,744
Noninterest income:
Other service charges, commissions and fees		5,554			4,853			16,725			14,326
Service charges on deposit accounts		4,595			4,838			12,993			14,498
Technology services		3,349			3,196			9,979			9,290
Income from origination and sale of loans		2,675			2,362			6,465			6,436
Income from fiduciary activities		1,574			1,434			4,692			4,251
Investment securities gains (losses), net		(1,811	)		(52	)		(2,941	)		(762	)
Other income		1,526			2,790			4,338			5,133
Total noninterest income		17,462			19,421			52,251			53,172
Noninterest expense:
Salaries, wages and employee benefits		20,353			19,124			59,189			55,124
Furniture and equipment		3,907			3,848			11,908			11,121
Occupancy, net		3,212			2,979			10,143			8,580
Mortgage servicing rights amortization expense		1,190			783			3,550			2,535
Mortgage servicing rights impairment expense		(985	)		1,180			(1,297	)		104
Professional fees		766			835			2,058			2,301
Outsourced technology services		625			727			1,703			1,848
Core deposit intangible amortization expense		253			275			760			841
Other expenses		7,821			7,809			23,167			22,977
Total noninterest expense		37,142			37,560			111,181			105,431
Income before income taxes		23,562			17,028			61,527			51,485
Income tax expense		8,288			5,942			21,414			18,109
Net income	$	15,274		$	11,086		$	40,113		$	33,376
Basic earnings per common share	$	1.91		$	1.41		$	5.03		$	4.23
Diluted earnings per common share	$	1.88		$	1.39		$	4.94		$	4.19

See accompanying notes to unaudited consolidated financial statements.

4

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

Consolidated Statements of Stockholders’ Equity and Comprehensive Income

(Dollars in thousands, except share and per share data)

(Unaudited)

							Unearned			Accumulated other			Total
	Common			Retained			compensation -			comprehensive			stockholders’
	stock			earnings			restricted stock			income (loss)			equity
Balance at December 31, 2004	$	36,803			275,172			(425	)		(3,224	)		308,326
Comprehensive income:
Net income		—			40,113			—			—			40,113
Unrealized losses on available-for-sale investment securities, net of income tax benefit of $2,600		—			—			—			(4,009	)		(4,009	)
Less reclassification adjustment for losses included in net income, net of income tax benefit of $1,157		—			—			—			1,784			1,784
Other comprehensive income														(2,225	)
Total comprehensive income														37,888
Common stock transactions:
52,907 shares retired		(3,331	)		—			—			—			(3,331	)
169,597 shares issued		10,100			—			—			—			10,100
1,500 shares issued pursuant to restricted stock plan		87			—			(87	)		—			—
1,000 shares cancelled pursuant to restricted stock plan		(65	)		—			65			—			—
Remeasurement of restricted stock awards		101			—			(101	)		—			—
Amortization of restricted stock awards		—			—			180			—			180
Cash dividends declared:
Common ($1.38 per share)		—			(10,997	)		—			—			(10,997	)
Balance at September 30, 2005	$	43,695			304,288			(368	)		(5,449	)		342,166
Balance at December 31, 2003	$	33,187			242,105			—			(1,066	)		274,226
Comprehensive income:
Net income		—			33,376			—			—			33,376
Unrealized losses on available-for-sale investment securities, net of income tax benefit of $293		—			—			—			(458	)		(458	)
Less reclassification adjustment for losses included in net income, net of income tax benefit of $297		—			—			—			465			465
Other comprehensive loss														7
Total comprehensive income														33,383
Common stock transactions:
84,237 shares retired		(4,463	)		—			—			—			(4,463	)
151,568 shares issued		8,073			—			—			—			8,073
11,000 shares issued pursuant to restricted stock plan		512			—			(512	)		—			—
Remeasurement of restricted stock awards		33			—			(33	)		—			—
Amortization of restricted stock awards		—			—			83			—			83
Cash dividends declared:
Common ($1.14 per share)		—			(9,003	)		—			—			(9,003	)
Balance at September 30, 2004	$	37,342			266,478			(462	)		(1,059	)		302,299

See accompanying notes to unaudited consolidated financial statements.

5

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

Consolidated Statements of Cash Flows

(Dollars in thousands)

(Unaudited)

	For the nine months
	ended September 30,
	2005			2004
Cash flows from operating activities:
Net income	$	40,113			33,376
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of joint ventures		(418	)		(234	)
Provision for loan losses		4,365			7,346
Depreciation		10,409			9,193
Amortization		4,310			3,376
Net premium amortization on investment securities		264			1,681
Net loss on sale of investment securities		2,941			762
Net gain on origination and sale of loans		(6,465	)		(6,436	)
Net loss (gain) on sale of property and equipment		(12	)		18
Net change in impairment reserves for mortgage servicing rights		(1,312	)		104
Net increase in cash surrender value of company-owned life insurance		(1,330	)		(1,257	)
Write-down of property pending disposal		21			—
Amortization of restricted stock awards		180			83
Deferred income taxes		194			(28	)
Changes in operating assets and liabilities:
Decrease in loans held for sale		6,726			34,640
Increase in interest receivable		(6,362	)		(2,827	)
Decrease (increase) in other assets		(2,101	)		1,916
Increase (decrease) in accrued interest payable		1,969			(138	)
Increase in accounts payable and accrued expenses		10,102			2,305
Net cash provided by operating activities		63,594			83,880
Cash flows from investing activities:
Purchases of investment securities:
Held-to-maturity		(9,281	)		(10,219	)
Available-for-sale		(1,056,907	)		(350,224	)
Proceeds from maturities and paydowns of investment securities:
Held-to-maturity		4,934			5,074
Available-for-sale		835,670			286,115
Proceeds from sales of available-for-sale investment securities		197,935			25,384
Net decrease in cash equivalent mutual funds classified as available-for-sale investment securities		177			—
Purchases and originations of mortgage servicing rights		(5,186	)		(5,104	)
Extensions of credit to customers, net of repayments		(248,705	)		(167,985	)
Recoveries of loans charged-off		1,487			1,536
Proceeds from sales of other real estate		2,943			1,535
Capital contribution to joint venture		(2,800	)		—
Net capital expenditures		(6,099	)		(17,428	)
Disposition of banking office, net of cash and cash equivalents		—			(19,537	)
Net cash used in investing activities		(285,832	)		(250,853	)
Cash flows from financing activities:
Net increase in deposits		155,434			112,483
Net increase in repurchase agreements		45,570			78,849
Net increase (decrease) in other borrowed funds		(1,560	)		914
Borrowings of long-term debt		11,500			24,975
Repayments of long-term debt		(16,409	)		(30,030	)
Net decrease in debt issuance costs		30			35
Proceeds from issuance of common stock		10,100			8,073
Payments to retire common stock		(3,331	)		(4,463	)
Dividends paid on common stock		(10,997	)		(9,003	)
Net cash provided by financing activities		190,337			181,833
Net increase (decrease) in cash and cash equivalents		(31,901	)		14,860
Cash and cash equivalents at beginning of period		355,908			281,442
Cash and cash equivalents at end of period	$	324,007		$	296,302

See accompanying notes to unaudited consolidated financial statements.

6

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES

Notes to Unaudited Consolidated Financial Statements

(Dollars in thousands, except share and per share data)

(1)	Basis of Presentation
	In the opinion of management, the accompanying unaudited consolidated financial statements of First Interstate BancSystem, Inc. (the “Parent Company” or “FIBS”) and subsidiaries (the “Company”) contain all adjustments (all of which are of a normal recurring nature) necessary to present fairly the financial position of the Company at September 30, 2005 and December 31, 2004 and the results of operations and cash flows for each of the three and nine month periods ended September 30, 2005 and 2004, in conformity with U.S. generally accepted accounting principles. The balance sheet information at December 31, 2004 is derived from audited consolidated financial statements, however, certain reclassifications, none of which were material, have been made to conform to the September 30, 2005 presentation.
	These consolidated financial statements should be read in conjunction with the audited consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2004. Operating results for the three and nine months ended September 30, 2005 are not necessarily indicative of the results that may be expected for the year ending December 31, 2005.
(2)	Stock-Based Compensation
	The Company has two stock-based employee compensation plans, the 2004 Restricted Stock Award Plan and the 2001 Stock Option Plan. The Company accounts for these plans under the recognition and measurement principles of Accounting Principles Board (“APB”) Opinion No. 25 (“APB No. 25”), “Accounting for Stock Issued to Employees,” and related interpretations. Compensation cost related to restricted stock awards is recorded each period from the date of grant to the measurement date based on the fair value of the Company’s common stock at the end of the period. Stock options granted pursuant to the 2001 Stock Option Plan have an exercise price equal to the fair value of the Company’s common stock at date of grant. Accordingly, the Company does not recognize compensation expense for stock option awards. The following table illustrates the effect on net income and earnings per share if compensation expense had been determined for stock option awards based on an estimate of fair value of the option at the date of grant consistent with Financial Accounting Standards Board (“FASB”) Statement of Financial Accounting Standard (“SFAS”) No. 123, “Accounting for Stock-Based Compensation,” as amended.

	Three months ended September 30,						Nine months ended September 30,
	2005			2004			2005			2004
Net income as reported	$	15,274		$	11,086		$	40,113		$	33,376
Deduct: total stock-based employee compensation expense determined using a fair value based method, net of tax effect		(107	)		(98	)		(332	)		(280	)
Pro forma net income	$	15,167		$	10,988		$	39,781		$	33,096
Basic earnings per share	$	1.91		$	1.41		$	5.03		$	4.23
Pro forma basic earnings per share	$	1.90		$	1.39		$	4.99		$	4.19
Diluted earnings per share	$	1.88		$	1.39		$	4.94		$	4.19
Pro forma diluted earnings per share	$	1.86		$	1.38		$	4.90		$	4.15

The fair value of options was estimated at the grant date using a Black-Scholes option pricing model, which requires the input of subjective assumptions. Because the Company’s common stock and stock options have characteristics significantly different from listed securities and traded options, and because changes in the subjective input assumptions can materially affect the fair value estimate, the existing models do not necessarily provide a reliable single measure of the fair value of stock options. The weighted average fair values of options granted during the nine months ended September 30, 2005 and 2004 were $6.03 and $6.44, respectively. Weighted average assumptions used in the valuation model include risk-free interest rates of 4.19% and 4.74% and expected stock price volatility of 8.4% and 7.8% for the nine months ended September 30, 2005 and 2004, respectively; and, expected lives of options of 8.5 years and dividend yields of 3.05% in 2005 and 2004.

7

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES
Notes to Unaudited Consolidated Financial Statements
(Dollars in thousands, except share and per share data)

(3)	Recent Accounting Pronouncements
	Accounting for Share-Based Payments. In December 2004, the FASB issued SFAS No. 123 (Revised 2004), “Share-Based Payments” (“SFAS No. 123R”), establishing accounting standards for a wide range of share-based compensation arrangements including stock options, restricted stock, performance-based stock awards, stock appreciation rights and employee stock purchase plans. SFAS No. 123R replaces existing requirements under SFAS No. 123 and eliminates the ability to account for share-based compensation transactions using APB No. 25. Effective April 21, 2005, the Securities and Exchange Commission amended the date for compliance with SFAS No. 123R to the first interim or annual reporting period of the first fiscal year beginning on or after June 15, 2005. The provisions of SFAS No. 123R are effective for the Company on January 1, 2006. The approximate impact of adoption of SFAS No. 123R is illustrated by the pro forma disclosure of net income and earnings per share included in Note 2 herein. However, the Company has not yet determined that it will continue to use a Black-Scholes pricing model upon the adoption of SFAS No. 123R. Additionally, expected stock price volatility assumptions used in pricing models have a significant impact on the estimated fair value of stock options. Because the Company’s common stock is not actively traded and there is no established trading market for the stock, the Company bases expected stock price volatility assumptions on the historical volatility of the Company’s common stock calculated using the quarterly appraised value of a minority interest over a ten-year period. The Company is currently re-evaluating assumptions used in estimating the fair value of stock options using guidance provided by SFAS No. 123R and subsequent interpretations.
	Accounting Changes and Error Corrections. On June 7, 2005, the FASB issued SFAS No. 154, “Accounting Changes and Error Corrections — a replacement of APB Opinion No. 20, Accounting Changes, and SFAS No. 3, Reporting Accounting Changes in Interim Financial Statements.” Under the provisions of SFAS No. 154, voluntary changes in accounting principles are applied retrospectively to prior periods’ financial statements unless it would be impractical. SFAS No. 154 supersedes APB Opinion No. 20, which required that most voluntary changes in accounting principles be recognized by including in the current period’s net income the cumulative effect of the change. SFAS No. 154 also makes a distinction between “retrospective application” of a change in accounting principle and the “restatement” of financial statements to reflect the correction of an error. The provisions of SFAS No. 154 are effective for accounting changes made in fiscal years beginning after December 15, 2005. The Company does not expect adoption to have a material impact on the consolidated financial statements, results of operations or liquidity of the Company.
(4)	Computation of Earnings per Share
	Basic earnings per common share (EPS) is calculated by dividing net income by the weighted average number of common shares outstanding during the period presented. Diluted earnings per common share is calculated by dividing net income by the weighted average number of common shares and potential common shares outstanding during the period.
	The following table sets forth the computation of basic and diluted earnings per share for the three and nine month periods ended September 30, 2005 and 2004.

	Three months ended September 30,				Nine months ended September 30,
	2005		2004		2005		2004
Net income basic and diluted	$	15,274	$	11,086	$	40,113	$	33,376
Average outstanding shares — basic		7,981,356		7,887,163		7,971,921		7,895,303
Add: effect of dilutive stock options		153,525		87,166		143,625		76,203
Average outstanding shares — diluted		8,134,881		7,974,329		8,115,546		7,971,506
Basic earnings per share	$	1.91	$	1.41	$	5.03	$	4.23
Diluted earnings per share	$	1.88	$	1.39	$	4.94	$	4.19

8

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES
Notes to Unaudited Consolidated Financial Statements
(Dollars in thousands, except share and per share data)

(5)	Financial Instruments with Off-Balance Sheet Risk
	The Company is a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit and standby letters of credit. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the commitment contract. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. At September 30, 2005, commitments to extend credit to existing and new borrowers approximated $824,778, which includes $162,576 on unused credit card lines and $214,713 with commitment maturities beyond one year.
	Standby letters of credit are conditional commitments issued by the Company to guarantee the performance of a customer to a third party. At September 30, 2005, the Company had outstanding standby letters of credit of $85,694. The estimated fair value of the obligation undertaken by the Company in issuing the standby letters of credit is included in other liabilities in the Company’s consolidated balance sheet.
(6)	Other Post Retirement Benefits
	The Company sponsors a contributory defined benefit healthcare plan (the “Plan”) for active employees and employees and directors retiring from the Company at the age of at least 55 years and with at least 15 years of continuous service. Retired Plan participants contribute the full cost of benefits based on the average per capita cost of benefit coverage for both active employees and retired Plan participants. A postretirement benefit obligation of $1,025 is included in other liabilities on the Company’s September 30, 2005 consolidated balance sheet. A transition asset, representing the difference between the accumulated postretirement benefit obligation and the fair value of plan assets at the date of transition, of $909 is included in other assets on the Company’s September 30, 2005 consolidated balance sheet. The transition asset is being amortized as a component of net periodic postretirement benefit cost on a straight line basis over the estimated average remaining service period of active plan participants of 16.3 years. Prior to May 2005, retired plan participants’ contributions were based solely on the average per capita cost of benefit coverage for retired Plan participants only. As such, no postretirement benefit obligation existed. The net periodic benefit cost of the Plan was not significant during any of the reported periods.
	The Medicare Prescription Drugs, Improvement and Modernization Act was signed into law in December 2003 and introduced a prescription drug benefit under Medicare as well as a federal subsidy to sponsors of retiree health care plans that provide a benefit that is at least actuarially equivalent to Medicare Part D. In accordance with FASB Staff Position 106-2, “Accounting and Disclosure Requirements Related to the Prescription Drug, Improvement and Modernization Act of 2003,” the Company has determined that the benefits it provides are not actuarially equivalent to Medicare Part D; therefore, the Company will not receive a federal subsidy.
(7)	Segment Reporting
	The Company has two operating segments, Community Banking and Technology Services. Community Banking encompasses commercial and consumer banking services offered to individuals, businesses and municipalities. Technology Services encompasses technology services provided to affiliated and non-affiliated financial institutions.
	The Other category includes the net funding cost and other expenses of the Parent Company, the operational results of non-bank subsidiaries (except the Company’s technology services subsidiary) and intercompany eliminations.

9

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES
Notes to Unaudited Consolidated Financial Statements
(Dollars in thousands, except share and per share data)

Selected segment information for the three and nine month periods ended September 30, 2005 and 2004 follows:

	Three months ended September 30, 2005
	Community		Technology
	Banking		Services		Other			Total
Net interest income (expense)	$	45,532	$	29	$	(944	)	$	44,617
Provision for loan losses		1,375		—		—			1,375
Net interest income (expense) after provision		44,157		29		(944	)		43,242
Noninterest income:
External sources		13,832		3,350		280			17,462
Internal sources		—		3,460		(3,460	)		—
Total noninterest income		13,832		6,810		(3,180	)		17,462
Noninterest expense		33,551		4,949		(1,358	)		37,142
Income (loss) before income taxes		24,438		1,890		(2,766	)		23,562
Income tax expense (benefit)		8,689		744		(1,145	)		8,288
Net income (loss)	$	15,749	$	1,146	$	(1,621	)	$	15,274
Depreciation and core deposit intangibles amortization	$	3,502	$	—	$	61		$	3,563

	Three Months Ended September 30, 2004
	Community		Technology
	Banking		Services		Other			Total
Net interest income (expense)	$	38,373	$	8	$	(827	)	$	37,554
Provision for loan losses		2,387		—					2,387
Net interest income (expense) after provision		35,986		8		(827	)		35,167
Noninterest income:
External sources		16,128		3,195		98			19,421
Other operating segments		—		3,430		(3,430	)		—
Total noninterest income		16,128		6,625		(3,332	)		19,421
Noninterest expense		34,389		4,966		(1,795	)		37,560
Income (loss) before income taxes		17,725		1,667		(2,364	)		17,028
Income tax expense (benefit)		6,195		663		(916	)		5,942
Net income (loss)	$	11,530	$	1,004	$	(1,448	)	$	11,086
Depreciation and core deposit amortization expense	$	3,379	$	—	$	49		$	3,428

10

FIRST INTERSTATE BANCSYSTEM, INC. AND SUBSIDIARIES
Notes to Unaudited Consolidated Financial Statements
(Dollars in thousands, except share and per share data)

	Nine Months Ended September 30, 2005
	Community		Technology
	Banking		Services		Other			Total
Net interest income (expense)	$	127,454	$	69	$	(2,701	)	$	124,822
Provision for loan losses		4,365		—		—			4,365
Net interest income (expense) after provision		123,089		69		(2,701	)		120,457
Noninterest income:
External sources		41,682		9,980		589			52,251
Internal sources		1		10,354		(10,355	)		—
Total noninterest income		41,683		20,334		(9,766	)		52,251
Noninterest expense		100,889		14,751		(4,459	)		111,181
Income (loss) before income taxes		63,883		5,652		(8,008	)		61,527
Income tax expense (benefit)		22,503		2,235		(3,324	)		21,414
Net income (loss)	$	41,380	$	3,417	$	(4,684	)	$	40,113
Depreciation and core deposit amortization expense	$	10,986	$	—	$	183		$	11,169

	Nine Months Ended September 30, 2004
	Community		Technology
	Banking		Services		Other			Total
Net interest income (expense)	$	113,457	$	16	$	(2,383	)	$	111,090
Provision for loan losses		7,346		—					7,346
Net interest income (expense) after provision		106,111		16		(2,383	)		103,744
Noninterest income:
External sources		43,652		9,290		230			53,172
Other operating segments		3		10,071		(10,074	)		—
Total noninterest income		43,655		19,361		(9,844	)		53,172
Noninterest expense		95,919		14,636		(5,124	)		105,431
Income (loss) before income taxes		53,847		4,741		(7,103	)		51,485
Income tax expense (benefit)		18,876		1,883		(2,650	)		18,109
Net income (loss)	$	34,971	$	2,858	$	(4,453	)	$	33,376
Depreciation and core deposit amortization expense	$	9,890	$	—	$	144		$	10,034

(8)	Commitments and Contingencies
	The Company had commitments under construction contracts of $2,504 as of September 30, 2005.
(9)	Supplemental Disclosures to Consolidated Statement of Cash Flows
	The Company paid cash of $42,143 and $30,947 for interest during the nine months ended September 30, 2005 and 2004, respectively. The Company paid cash for income taxes of $17,597 and $16,133 during the nine months ended September 30, 2005 and 2004, respectively.

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Item 2.

MANAGEMENT’S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS

     The following discussion should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2004, including the audited financial statements contained therein, filed with the Securities and Exchange Commission.

FORWARD LOOKING STATEMENTS

     Certain statements contained in this document that are not statements of historical fact constitute “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. Words such as “believes,” “anticipates,” “expects,” “intends,” “plans” and similar expressions are intended to identify forward-looking statements but are not the exclusive means of identifying such statements. Forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause the actual results, performance or achievements of the Company to be materially different from any future results, performance or achievements expressed or implied by such statements. Such factors include, among others, the following: general economic and business conditions in those areas in which the Company operates; demographic changes; competition; fluctuations in interest rates; changes in business strategy or development plans; changes in governmental regulation; credit quality; the availability of capital to fund the expected expansion of the Company’s business; and, other factors identified in the Company’s Annual Report on Form 10-K for the year ended December 31, 2004, including, without limitation, information under the caption “Business — Risk Factors” included in Part I, Item 1. Given these uncertainties, shareholders and prospective investors are cautioned not to place undue reliance on such forward-looking statements. Forward-looking statements speak only as of the date on which such statements are made. The Company disclaims any obligation to update any such factors or to publicly announce the results of any revisions to any of the forward-looking statements contained herein to reflect future events or developments.

CRITICAL ACCOUNTING ESTIMATES AND SIGNIFICANT ACCOUNTING POLICIES

     The Company’s consolidated financial statements are prepared in accordance with U.S. generally accepted accounting principles and follow general practices within the industries in which it operates. Application of these principles requires management to make estimates, assumptions and judgments that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ significantly from those estimates.

     The Company’s accounting policies are fundamental to understanding Management’s Discussion and Analysis of Financial Condition and Results of Operations. The most significant accounting policies followed by the Company are presented in Note 1 of the Notes to Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2004.

     The Company has identified the allowance for loan losses and the valuation of mortgage servicing rights as critical accounting estimates because they require management to make particularly difficult, subjective and/or complex judgments about matters that are inherently uncertain, and changes in the estimates that are reasonably likely to occur from period to period, or the use of different estimates that management could have reasonably used in the current period, would have a material impact on the Company’s consolidated financial statements, results of operations or liquidity.

     The allowance for loan losses represents management’s estimate of probable credit losses inherent in the loan portfolio. Determining the amount of the allowance for loan losses is considered a critical accounting estimate because it requires significant judgment and the use of subjective measurements, including management’s assessment of the internal risk classifications of loans, changes in the nature of the loan portfolio, industry concentrations and the impact of current local, regional and national economic factors on the quality of the loan portfolio, all of which may be susceptible to significant change. Note 1 of the Notes to Consolidated Financial Statements in the Company’s Annual Report on Form 10-K for the year ended December 31, 2004 describes the methodology used to determine the allowance for loan losses. A discussion of the factors driving changes in the amount of the allowance for loan losses is included herein.

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     The Company utilizes the expertise of a third-party consultant to estimate quarterly the fair value of its mortgage servicing rights. In evaluating the mortgage servicing rights, the consultant uses discounted cash flow modeling techniques, which require estimates regarding the amount and timing of expected future cash flows, including assumptions about loan repayment rates, costs to service, as well as interest rate assumptions that contemplate the risk involved. Management believes the valuation techniques and assumptions used by the consultant are reasonable. Management considers the determination of the fair value of mortgage servicing rights to be a critical accounting estimate because of the assets’ sensitivity to changes in estimates and assumptions used, particularly loan repayment rates and discount rates. Notes 1 and 7 of the Notes to Consolidated Financial Statements in the Company’s Annual Report on Form 10-K for the year ended December 31, 2004 describe the methodology used to determine fair value of mortgage servicing rights.

EXECUTIVE OVERVIEW

     During the first nine months of 2005, the Company remained focused on improving internal efficiency and generating additional revenue through sales initiatives and pricing opportunities. The Company reported net income of $15.3 million, or $1.88 per diluted share, for the quarter ended September 30, 2005 as compared to $11.1 million, or $1.39 per diluted share, for the same period in 2004. For the nine months ended September 30, 2005, the Company reported net income of $40.1 million, or $4.94 per diluted share, as compared to $33.4 million, or $4.19 per diluted share, for the same period in 2004. Quarter-to-date and year-to-date improvements in earnings were primarily due to higher net interest income, largely the result of internal loan growth, higher yields on interest earning assets and lower provisions for loan losses in the current year. Noninterest income for the three and nine months ended September 30, 2005 decreased 10.1% and 1.7%, respectively, from the same periods in the prior year primarily due to a $1.7 million gain on the sale of a branch banking office recorded during third quarter 2004 and investment securities losses recorded in third quarter 2005. Noninterest expense decreased 1.1% during the three months ended September 30, 2005 and increased 5.5% during the nine months ended September 30, 2005 as compared to the same periods in the prior year. Quarter-over-quarter decreases are primarily due to fluctuations in impairment of capitalized mortgage servicing rights. Year-over-year decreases in other expenses resulting from fluctuations in impairment of capitalized mortgage servicing rights were more than offset primarily by annual merit increases in salaries, wages and benefits expenses and higher occupancy and depreciation costs associated with the addition and renovation of banking facilities.

     During first quarter 2005, the Company made a strategic decision to discontinue the operation of nine branch banking offices located inside Wal-Mart stores. As of June 30, 2005, operations at five of the nine Wal-Mart in-store branch banking offices had been discontinued and customer loan and deposit accounts had been transferred to existing branch banking offices located in the same communities. Management expects the discontinuation of operations at the four remaining Wal-Mart in-store branch banking offices and recognition of all resulting expenses will be completed during first quarter 2006. During the nine months ended September 30, 2005, the Company recorded expenses of $952 thousand directly related to the discontinuation of operations, including lease termination fees and estimated costs to restore leased facilities to their original condition of $375 thousand, acceleration of depreciation on leasehold improvements and equipment attached to the premises of $503 thousand, and accruals for employment incentive awards of $74 thousand .

     The Company currently holds a minority equity interest in an unconsolidated joint venture entity that has engaged a financial advisor to explore strategic alternatives designed to maximize its equity value. The Company was informed in September, 2005 that the entity has received and is evaluating a non-binding acquisition proposal from a third party, but has not entered into a binding letter of intent or other agreement. If the current acquisition proposal were ultimately consummated, of which there can be no assurance, it is possible that the Company will realize a one-time, after-tax gain in the range of approximately $5 to $10 million.

RESULTS OF OPERATIONS

     Net Interest Income. Net interest income, the Company’s largest source of operating income, is derived from interest, dividends and fees received on interest earning assets, less interest expense incurred on interest bearing liabilities. The most significant impact on the Company’s net interest income between periods is derived from the interaction of changes in the volume of and rates earned or paid on interest earning assets and interest bearing liabilities (“spread”). The volume of loans, investment securities and other interest earning assets, compared to the volume of interest bearing deposits and indebtedness, combined with the spread, produces changes in the net interest income between periods.

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     The following tables present, for the periods indicated, condensed average balance sheet information for the Company, together with interest income and yields earned on average interest earning assets and interest expense and rates paid on average interest bearing liabilities.

Average Balance Sheets, Yields and Rates
(Dollars in thousands)

	Three months ended September 30,
	2005								2004
	Average					Average			Average					Average
	Balance		Interest			Rate			Balance		Interest			Rate
Interest earning assets:
Loans (1)	$	2,929,238		52,021			7.05	%	$	2,651,383		40,770			6.12	%
Investment securities (1)		894,369		9,382			4.16			799,916		7,847			3.90
Federal funds sold		85,949		772			3.56			75,508		279			1.47
Interest bearing deposits in banks		7,623		59			3.07			5,805		26			1.78
Total interest earning assets		3,917,179		62,234			6.30	%		3,532,612		48,922			5.51	%
Noninterest earning assets		452,542								466,280
Total assets	$	4,369,721							$	3,998,892
Interest bearing liabilities:
Demand deposits	$	671,064		1,284			0.76	%	$	573,701		408			0.28	%
Savings deposits		903,279		2,999			1.32			911,239		1,740			0.76
Time deposits		1,016,270		7,756			3.03			1,013,937		6,365			2.50
Federal funds purchased		70		1			3.29			—		—		NA
Borrowings(2)		508,627		3,417			2.67			394,295		1,024			1.03
Long-term debt		62,124		640			4.09			46,057		539			4.66
Subordinated debenture		41,238		709			6.82			41,238		513			4.95
Total interest bearing liabilities		3,202,672		16,806			2.08	%		2,980,467		10,589			1.41	%
Noninterest bearing deposits		800,332								703,804
Other noninterest bearing liabilities		35,543								30,784
Stockholders’ equity		331,174								283,837
Total liabilities & stockholders’ equity	$	4,369,721							$	3,998,892
Net FTE interest income			$	45,428							$	38,333
Less FTE adjustments				(811	)							(779	)
Net interest income from consolidated statements of income			$	44,617							$	37,554
Interest rate spread							4.22	%							4.10	%
Net FTE yield on interest earning assets(3)							4.60	%							4.32	%

(1)	Interest income and average rates for tax exempt loans and securities are presented on a fully-taxable equivalent (“FTE”) basis.
(2)	Includes interest on federal funds purchased, securities sold under repurchase agreements and other borrowed funds. Excludes long-term debt.
(3)	Net FTE yield on interest earning assets during the period equals (i) the difference between annualized interest income on interest earning assets and annualized interest expense on interest bearing liabilities, divided by (ii) average interest earning assets for the period.

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Average Balance Sheets, Yields and Rates
(Dollars in thousands)

	Nine months ended September 30,
	2005								2004
	Average					Average			Average					Average
	Balance		Interest			Rate			Balance		Interest			Rate
Interest earning assets:
Loans (1)	$	2,833,364		142,535			6.73	%	$	2,609,297		119,742			6.13	%
Investment securities (1)		872,720		26,672			4.09			813,154		23,823			3.91
Federal funds sold		80,201		1,829			3.05			53,336		498			1.25
Interest bearing deposits in banks		19,104		363			2.54			2,236		33			1.97
Total interest earning assets		3,805,389		171,399			6.02	%		3,478,023		144,096			5.53	%
Noninterest earning assets		454,723								455,794
Total assets	$	4,260,112							$	3,933,817
Interest bearing liabilities:
Demand deposits	$	641,200		2,798			0.58	%	$	568,478		1,119			0.25	%
Savings deposits		905,966		7,574			1.12			889,770		4,746			0.69
Time deposits		1,008,502		21,309			2.82			1,028,551		19,496			2.55
Federal funds purchased		1,012		23			3.04			4,515		33			0.98
Borrowings(2)		491,610		8,484			2.31			367,684		2,180			0.66
Long-term debt		63,073		1,954			4.14			48,654		1,668			4.55
Subordinated debenture		41,238		1,970			6.39			41,238		1,424			4.44
Total interest bearing liabilities		3,152,601		44,112			1.87	%		2,948,890		30,666			1.38	%
Noninterest bearing deposits		756,186								671,814
Other noninterest bearing liabilities		32,553								30,272
Stockholders’ equity		318,772								282,841
Total liabilities & stockholders’ equity	$	4,260,112							$	3,933,817
Net FTE interest income			$	127,287							$	113,430
Less FTE adjustments				(2,465	)							(2,340	)
Net interest income from consolidated statements of income			$	124,822							$	111,090
Interest rate spread							4.15	%							4.15	%
Net FTE yield on interest earning assets(3)							4.47	%							4.36	%

(1)	Interest income and average rates for tax exempt loans and securities are presented on a fully-taxable equivalent (“FTE”) basis.
(2)	Includes interest on federal funds purchased, securities sold under repurchase agreements and other borrowed funds. Excludes long-term debt.
(3)	Net FTE yield on interest earning assets during the period equals (i) the difference between annualized interest income on interest earning assets and annualized interest expense on interest bearing liabilities, divided by (ii) average interest earning assets for the period.

     Net interest income, on a fully taxable equivalent (“FTE”) basis, increased $7.1 million, or 18.5%, to $45.4 million for the three months ended September 30, 2005 as compared to $38.3 million for the same period in 2004. During the nine month period ended September 30, 2005, FTE net interest income increased $13.9 million, or 12.2%, to $127.3 million as compared to $113.4 million for the same period in 2004. Quarter-to-date and year-to-date increases in FTE net interest margin as compared to the same periods in 2004 are primarily the result of internal loan growth (principally commercial real estate, indirect consumer and construction loans) combined with higher yields earned on loans and investment securities. Average interest earning assets increased 10.9% and 9.4% for the three and nine months ended September 30, 2005, respectively, as compared to the same periods in the prior year. Increases in FTE net interest income were partially offset by

15

higher funding costs, the result of increases in market interest rates. The FTE net interest margin ratio increased 28 basis points to 4.60% for the three months ended September 30, 2005 as compared to 4.32% for the same period in the prior year and 11 basis points to 4.47% for the nine months ended September 30, 2005 as compared to 4.36% for the same period in the prior year.

     The table below sets forth, for the periods indicated, a summary of the changes in interest income and interest expense resulting from estimated changes in average asset and liability balances (“volume”) and estimated changes in average interest rates (“rate”). Changes which are not due solely to volume or rate have been allocated to these categories based on the respective percent changes in average volume and average rate as they compare to each other.

Analysis of Interest Changes Due To Volume and Rates
(Dollars in thousands)

	Three months ended September 30,								Nine months ended September 30,
	2005 compared with 2004								2005 compared with 2004
	Volume			Rate			Net		Volume			Rate			Net
Interest earning assets:
Loans(1)	$	4,284			6,967			11,251		10,273			12,520			22,793
Investment securities(1)		929			606			1,535		1,744			1,105			2,849
Interest bearing deposits in banks		8			25			33		249			81			330
Federal funds sold		39			454			493		251			1,080			1,331
Total change		5,260			8,052			13,312		12,517			14,786			27,303
Interest bearing liabilities:
Demand deposits		69			807			876		143			1,536			1,679
Savings deposits		(15	)		1,274			1,259		86			2,742			2,828
Time deposits		15			1,376			1,391		(381	)		2,194			1,813
Federal funds purchased		—			1			1		(26	)		16			(10	)
Borrowings(2)		298			2,095			2,393		735			5,569			6,304
Long-term debt		189			(88	)		101		494			(208	)		286
Subordinated debenture		—			196			196		—			546			546
Total change		556			5,661			6,217		1,051			12,395			13,446
Increase (decrease) in FTE net interest income	$	4,704			2,391			7,095		11,466			2,391			13,857

(1)	Interest income and average rates for tax exempt loans and securities are presented on a FTE basis.
(2)	Includes interest on federal funds purchased, securities sold under repurchase agreements and other borrowed funds.

     Noninterest Income. The Company’s principal sources of noninterest income include other service charges, commissions and fees; service charges on deposit accounts; technology services revenues; income from the origination and sale of loans; and, income from fiduciary activities. Noninterest income decreased $2.0 million, or 10.1%, to $17.5 million for the three months ended September 30, 2005 as compared to $19.4 million for the same period in 2004 and $921 thousand, or 1.7%, to $52.3 million for the nine months ended September 30, 2005 as compared to $53.2 million for the same period in 2004. Significant components of these decreases are discussed below.

     Other service charges, commissions and fees primarily include debit and credit card interchange income, mortgage servicing fees, investment services revenues and ATM service charge revenues. Other service charges, commissions and fees increased $701 thousand, or 14.4%, to $5.6 million for the three months ended September 30, 2005 as compared to $4.9 million for the same period in 2004 and $2.4 million, or 16.7%, to $16.7 million for the nine months ended September 30, 2005 as compared to $14.3 million for the same period in 2004 primarily due to increases in debit and credit card interchange income resulting from higher transaction volumes and increases in mortgage servicing fees resulting from increases in the principal balance of loans serviced.

     Service charges on deposit accounts decreased $243 thousand, or 5.0%, to $4.6 million for the three months ended September 30, 2005 as compared to $4.8 million for the same period in 2004 and $1.5 million, or 10.4%, to $13.0 million for the nine months ended September 30, 2004 as compared to $14.5 million for the same period in 2004. Quarter-to-date and

16

year-to-date decreases were primarily due to fewer overdrafts. In addition, service charges on cash management deposit accounts decreased during the three and nine months ended September 30, 2005 as compared to the same periods in 2004 primarily due to higher earnings credit rates. The earnings credit rate, which is based on market interest rates, reflects the value of deposit balances maintained by cash management customers. The earnings credit is used to offset service charges incurred by cash management customers. Because market interest rates have trended upward since mid 2004, the earnings credit offset to service charges on cash management deposits is higher relative to 2004.

     Technology services revenues increased $153 thousand, or 4.8%, to $3.3 million for the three months ended September 30, 2005 as compared to $3.2 million for the same period in 2004 and $689 thousand, or 7.4%, to $10.0 million for the nine months ended September 30, 2005 as compared to $9.3 million for the same period in 2004 primarily due to increases in the number of accounts and volume of transactions processed by the Company’s core data services.

     Income from the origination and sale of loans includes origination and processing fees on residential real estate loans held for sale and gains on residential real estate loans sold to third parties. Fluctuations in market interest rates have a significant impact on the level of income generated from the origination and sale of loans. Higher interest rates can substantially reduce the demand for home loans and loans to refinance existing mortgages. Conversely, lower interest rates generally stimulate home loan origination and refinancing. Income from the origination and sale of loans increased $313 thousand, or 13.3%, to $2.7 million for the three months ended September 30, 2005 as compared to $2.4 million for the same period in 2004 and $29 thousand, or less than 1.0%, to $6.5 million for the nine months ended September 30, 2005 as compared to $6.4 million for the same period in 2004.

     Revenues from fiduciary activities, comprised principally of fees earned for management of trust assets, increased $140 thousand, or 9.8%, to $1.6 million for the three months ended September 30, 2005 as compared to $1.4 million for the same period in 2004 and $441 thousand, or 10.4%, to $4.7 million for the nine months ended September 30, 2005 as compared to $4.3 million for the same period in 2004. Quarter-to-date and year-to-date increases are primarily due to higher asset management fees resulting from improved market performance of underlying trust account assets and the addition of new trust customers.

     The Company recorded net losses of $1.8 million on sales of investment securities during the three months ended September 30, 2005 as compared to net losses on sales of $52 thousand for the same period in 2004 and recorded net losses of $2.9 million during the nine months ended September 30, 2005 as compared to net losses of $762 thousand for the same period in 2004. Lower yielding U.S. government agency securities were sold and the proceeds were reinvested in higher yielding mortgage-backed and U.S. government agency securities.

     Other income primarily includes increases in the cash surrender value of company-owned life insurance, check printing income, agency stock dividends and gains on sales of assets other than investment securities. Other income decreased $1.3 million, or 45.3%, to $1.5 million for the three months ended September 30, 2005 as compared to $2.8 million for the same period in 2004 and $795 thousand, or 15.5%, to $4.3 million for the nine months ended September 30, 2005 as compared to $5.1 million for the same period in 2004. During third quarter 2004, the Company recorded a $1.7 million gain on the sale of a branch banking office. Quarter-to-date and year-to-date decreases in other income were partially offset by increases in the cash surrender value of company-owned life insurance; increases in earnings on securities held in trust under deferred compensation plans; and, gains on the sale of other real estate owned.

     Noninterest Expense. Noninterest expense decreased $418 thousand, or 1.1%, to $37.1 million for the three months ended September 30, 2005 as compared to $37.6 million for the same period in 2004 and increased $5.8 million, or 5.5%, to $111.2 million for the nine months ended September 30, 2005 as compared to $105.4 million for the same period in 2004. Significant components of the quarter-to-date decrease and year-to-date increase are discussed below.

     Salaries, wages and employee benefits expense increased $1.2 million, or 6.4%, to $20.4 million for the three months ended September 30, 2005 as compared to $19.1 million for the same period in 2004 and $4.1 million, or 7.4%, to $59.2 million for the nine months ended September 30, 2005 as compared to $55.1 million for the same period in 2004 primarily due to normal, annual merit increases and higher accruals for incentive bonuses. During the three and nine months ended September 30, 2005, the Company recorded employment incentives of $27 thousand and $74 thousand, respectively, for employees of the Wal-Mart in-store branches scheduled for closure.

     Furniture and equipment expenses increased $59 thousand, or 1.5%, to $3.9 million for the three months ended September 30, 2005 as compared to $3.8 million for the same period in 2004 and $787 thousand, or 7.1%, to $11.9 million for the nine months ended September 30, 2005 as compared to $11.1 million for the same period in 2004. The Company accelerated the depreciation of equipment at Wal-Mart in-store branch banking offices to the date of their expected closures resulting in additional expense of $17 thousand and $118 thousand during the three and nine months ended September

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30, 2005, respectively. The remaining year-to-date increase is primarily due to expenses associated with furnishing new facilities and upgrading existing facilities.

     Occupancy expense increased $233 thousand, or 7.8%, to $3.2 million for the three months ended September 30, 2005 as compared to $3.0 million for the same period in 2004 and $1.6 million, or 18.2%, to $10.1 million for the nine months ended September 30, 2005 as compared to $8.6 million for the same period in 2004. The Company accelerated the depreciation of leasehold improvements at Wal-Mart in-store branch banking offices to the date of their expected closure resulting in additional expense of $56 thousand and $385 thousand during the three and nine months ended September 30, 2005, respectively. The remaining quarter-to-date and year-to-date increases over the prior year are primarily due to depreciation and other expenses associated with the addition of new facilities and higher depreciation expense associated with upgrades of existing facilities.

     Mortgage servicing rights are amortized in proportion to and over the period of estimated net servicing income. Changes in estimated servicing period and growth in the serviced loan portfolio cause amortization expense to vary between periods. Mortgage servicing rights amortization increased $407 thousand, or 52.0%, to $1.2 million for the three months ended September 30, 2005 as compared to $783 thousand for the same period in 2004 and $1.0 million, or 40.0%, to $3.6 million for the nine months ended September 30, 2005 as compared to $2.5 million for the same period in 2004.

     Mortgage servicing rights are evaluated quarterly for impairment by discounting the expected future cash flows, taking into consideration the estimated level of prepayments based on current industry expectations and the predominant risk characteristics of the underlying loans. Impairment adjustments are recorded through a valuation allowance. The valuation allowance is adjusted for changes in impairment through current period earnings. The Company reversed $985 thousand and $1.2 million of previously recorded impairment related to mortgage servicing rights during the three and nine months ended September 30, 2005, respectively, as compared to recording additional impairment expense of $1.2 million and $104 thousand during the same respective periods in the prior year. The Company recorded permanent impairment of $15 thousand during the three and nine months ended September 2005. No permanent impairment was recorded during the three or nine months ended September 30, 2004.

     Income Tax Expense. The Company’s effective combined federal and state income tax rate was 34.8% and 35.2% for the nine months ended September 30, 2005 and 2004, respectively. The lower effective tax rate in the current year as compared to the prior year is primarily due to higher volumes of tax exempt municipal securities and other tax-credit qualified investments.

OPERATING SEGMENT RESULTS

     The Company’s primary operating segment is Community Banking. The Community Banking segment represented over 90% of the combined revenues and income of the Company during the three and nine months ended September 30, 2005 and 2004, and the consolidated assets of the Company as of September 30, 2005 and December 31, 2004.

     The following table summarizes net income (loss) for each of the Company’s operating segments.

Operating Segment Results
(Dollars in thousands)

Net Income (Loss)

	Net Income (Loss)
	Three months ended September 30,						Nine months ended September 30,
	2005			2004			2005			2004
Community Banking	$	15,749			11,530			41,380			34,971
Technology Services		1,146			1,004			3,417			2,858
Other		(1,621	)		(1,448	)		(4,684	)		(4,453	)
Total	$	15,274			11,086			40,113			33,376

     Net income from the Community Banking operating segment increased $4.2 million, or 36.6%, to $15.7 million for the three months ended September 30, 2005 as compared to $11.5 million for the same period in the prior year. For the nine months ended September 30, 2005, net income from the Community Banking operating segment increased $6.4 million, or 18.3%, to $41.4 million as compared to $35.0 million for the same period in 2004. Quarter-to-date and year-to-date increases from the prior year are primarily due to higher net interest income, the combined effect of internal growth and higher yields on loans and investment securities; and, lower provisions for loan losses. These increases were partially offset

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by losses on sales of investment securities; normal, annual merit increases in salaries and benefits expenses; fluctuations in amortization and level of impairment of capitalized mortgage servicing rights; higher occupancy expenses associated with the addition of new branch banking offices and the upgrade of existing branch banking offices; and, expenses related to the discontinuation of operations at Wal-Mart in-store branch banking offices.

     Net income from the Technology Services operating segment increased $142 thousand, or 14.1%, to $1.1 million for the three months ended September 30, 2005 as compared to $1.0 million for the same period in the prior year and $559 thousand, or 19.6%, to $3.4 million for the nine months ended September 30, 2005 as compared to $2.9 million for the same period in 2004 primarily due to increases in the number of accounts and volume of transactions processed by the Company’s core data services.

     Other net losses increased $173 thousand, or 11.9%, to $1.6 million for the three months ended September 30, 2005 as compared to $1.4 million for the same period in the prior year and $231 thousand, or 5.2%, to $4.7 million for the nine months ended September 30, 2005 as compared to $4.5 million for same period in the prior year primarily due to higher funding costs associated with Parent Company variable rate junior subordinated debentures and normal, annual merit increases in salaries, wages and employee benefits expenses.

FINANCIAL CONDITION

     Loans. Total loans increased $242.8 million, or 8.9%, to $2,982.3 million as of September 30, 2005 from $2,739.5 million as of December 31, 2004 due to internal growth. All major categories of loans, except residential real estate and commercial loans, increased from December 31, 2004. The largest growth occurred in commercial real estate and indirect consumer loans. Management attributes the Company’s loan growth to its strategic focus on internal growth within the Company’s market areas. While each loan originated must meet minimum underwriting standards established in the Company’s credit policies, lending officers are granted certain levels of autonomy in approving and pricing loans to assure that the banking offices are responsive to competitive issues and community needs in each market area.

     Investment Securities. The Company’s investment portfolio is managed to attempt to obtain the highest yield while meeting the Company’s risk tolerance and liquidity needs and satisfying pledging requirements for deposits of state and political subdivisions and securities sold under repurchase agreements. Investment securities increased $20.6 million, or 2.4%, to $887.9 million as of September 30, 2005 from $867.3 million as of December 31, 2004. The Company evaluates its investment portfolio quarterly for other-than-temporary declines in the market value of individual investment securities. This evaluation includes monitoring credit ratings; market, industry and corporate news; volatility in market prices; and, determining whether the market value of a security has been below its cost for an extended period of time. As of September 30, 2005, the Company had investment securities with fair values of $230.8 million that had been in a continuous loss position more than twelve months. Gross unrealized losses on these securities totaled $5.4 million as of September 30, 2005 and were primarily attributable to changes in interest rates. The Company recorded no impairment losses during the three or nine months ended September 30, 2005 and 2004.

     Accrued Interest Receivable. Accrued interest receivable increased $6.4 million, or 30.9%, to $26.9 million as of September 30, 2005 from $20.6 million as of December 31, 2004 primarily due to increases in average interest earning asset balances combined with higher yields on interest earning assets.

     Mortgage Servicing Rights. The Company recognizes the rights to service mortgage loans for others whether acquired or internally originated. Mortgage servicing rights, net of impairment reserves, increased $2.9 million, or 16.6%, to $20.6 as of September 30, 2005 from $17.6 million as of December 31, 2004 primarily due to internal loan origination. Impairment reserves for mortgage servicing rights were $3.3 million as of September 30, 2005 and $4.7 million as of December 31, 2004.

     Deferred Tax Asset. Deferred tax asset of $3.2 million as of September 30, 2005 increased $1.3 million, or 65.5%, from $1.9 million as of December 31, 2004 primarily due to fluctuations in unrealized losses on available-for-sale investment securities.

     Deposits. The Company emphasizes developing total client relationships with its customers in order to increase its core deposit base, which is the Company’s primary funding source. The Company’s deposits consist primarily of noninterest bearing and interest bearing demand deposits, savings, individual retirement and time deposit accounts. Total deposits increased $155.4 million, or 4.7%, to $3,477.1 million as of September 30, 2005 from $3,321.7 million as of December 31, 2004 primarily due to internal growth in noninterest bearing demand and interest bearing demand deposits.

     Repurchase Agreements. In addition to deposits, repurchase agreements with primarily commercial depositors provide an additional source of funds for the Company. Under repurchase agreements, deposit balances are invested in short-

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term U.S. government agency securities overnight and are then repurchased the following day. All outstanding repurchase agreements are due in one day. Repurchase agreements increased $45.6 million, or 10.1%, to $495.3 million as of September 30, 2005 from $449.7 million as of December 31, 2004 primarily due to high balances maintained by one large commercial customer. Increases in repurchase agreements were used, in part, to fund investment securities growth.

     Accrued Interest Payable. Accrued interest payable increased $2.0 million, or 20.7%, to $11.5 million as of September 30, 2005 from $9.5 million as of December 31, 2004 primarily due to increases in average interest bearing liability balances combined with higher interest costs on interest bearing liabilities.

     Accounts Payable and Accrued Expenses. Accounts payable and accrued expenses increased $10.1 million, or 59.8%, to $27.0 million as of September 30, 2005 from $16.9 million as of December 31, 2004 primarily due to timing of corporate income tax payments.

ASSET QUALITY

     Non-performing Assets. Non-performing assets include loans past due 90 days or more and still accruing interest, nonaccrual loans, loans renegotiated in troubled debt restructurings and other real estate owned (“OREO”).

     The following table sets forth information regarding non-performing assets as of the dates indicated:

Non-Performing Assets
(Dollars in thousands)

	Sept. 30,			Jun. 30,			Mar. 31,			Dec. 31,			Sept. 30,
	2005			2005			2005			2004			2004
Non-performing loans:
Nonaccrual loans	$	16,767			19,457			16,189			17,585			22,438
Accruing loans past due 90 days or more		2,716			2,668			3,490			905			1,474
Restructured loans		1,358			1,381			1,383			1,384			1,397
Total non-performing loans		20,841			23,506			21,062			19,874			25,309
OREO		728			1,290			2,701			1,828			1,647
Total non-performing assets	$	21,569			24,796			23,763			21,702			26,956
Non-performing assets to total loans and OREO		0.72	%		0.86	%		0.86	%		0.79	%		1.01	%

     Accruing loans past due 90 days or more increased $1.8 million, or 200.1%, to $2.7 million as of September 30, 2005 from $905 thousand as of December 31, 2004 primarily due to the loans of three commercial borrowers in the process of renewal.

     OREO decreased $1.1 million, or 60.2%, to $728 thousand as of September 30, 2005 from $1.8 million as of December 31, 2004 primarily due to the sale of four properties.

     Provision/Allowance for Loan Losses. The Company performs a quarterly assessment of the risks inherent in its loan portfolio, as well as a detailed review of each significant asset with identified weaknesses. Based on this analysis, the Company records a provision for loan losses in order to maintain the allowance for loan losses at a level considered sufficient to provide for known and inherent losses within the loan portfolio at each balance sheet date. Fluctuations in the provision for loan losses result from management’s assessment of the adequacy of the allowance for loan losses. The provision for loan losses decreased $1.0 million, or 42.4%, to $1.4 million for the three months ended September 30, 2005 as compared to $2.4 million for the same period in the prior year and $3.0 million, or 40.6%, to $4.4 million for the nine months ended September 30, 2005 as compared to $7.3 million for the same period in 2004. Lower provisions for loan losses in 2005 as compared to 2004 reflect positive trends in several important credit quality measures including levels of internally classified loans, improvement in average nonaccrual and past due loans as a percentage of total average loans and improvement in local economic factors. The allowance for loan losses was $43.2 million, or 1.45% of total loans, as of September 30, 2005 as compared to $42.1 million, or 1.54% of total loans, at December 31, 2004.

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     The following table sets forth information regarding the Company’s allowance for loan losses as of and for the periods indicated.

Allowance for Loan Losses

(Dollars in thousands)

	Three months ended
	Sept. 30,			Jun. 30,			Mar. 31,			Dec. 31,			Sept. 30,
	2005			2005			2005			2004			2004
Balance at beginning of period	$	43,368			42,660			42,141			42,396			41,174
Provision charged to operating expense		1,375			1,365			1,625			1,387			2,387
Less loans charged off		(1,990	)		(1,092	)		(1,698	)		(2,373	)		(1,673	)
Add back recoveries of loans previously charged off		460			435			592			731			508
Net loans charged-off		(1,530	)		(657	)		(1,106	)		(1,642	)		(1,165	)
Balance at end of period	$	43,213			43,368			42,660			42,141			42,396
Period end loans	$	2,982,325			2,891,674			2,769,056			2,739,509			2,674,963
Average loans		2,929,238			2,830,362			2,740,492			2,690,004			2,651,383
Annualized net loans charged off to average loans		0.21	%		0.09	%		0.16	%		0.24	%		0.17	%
Allowance to period end loans		1.45	%		1.50	%		1.54	%		1.54	%		1.58	%

CAPITAL RESOURCES

     A significant source of strength of a financial institution is its stockholders’ equity. Stockholders’ equity is influenced primarily by earnings, dividends and, to a lesser extent, sales and redemptions of common stock and changes in the unrealized holding gains or losses, net of taxes, on available-for-sale investment securities. Stockholders’ equity increased $33.8 million, or 11.0%, to $342.2 million as of September 30, 2005 from $308.3 million as of December 31, 2004 primarily due to retention of earnings. At September 30, 2005, the Company and its bank subsidiary each exceeded the “well-capitalized” requirements issued by the Federal Reserve Board.

     The Company paid dividends of $0.42 per common share during the first quarter of 2005 and $0.48 per common share during each of the second and third quarters of 2005, as compared to dividends of $0.34 per common share during the first quarter of 2004 and $0.40 per common share during each of the second and third quarters of 2004.

ASSET LIABILITY MANAGEMENT

     The primary objective of the Company’s asset liability management process is to optimize net interest income while prudently managing balance sheet risks by understanding the levels of risk accompanying its decisions and monitoring and managing these risks. The ability to optimize net interest margin is largely dependent on the achievement of an interest rate spread that can be managed during periods of fluctuating interest rates. Interest sensitivity is a measure of the extent to which net interest income will be affected by market interest rates over a period of time. Interest rate sensitivity is related to the difference between amounts of interest earning assets and interest bearing liabilities that reprice or mature within a given period of time. Management monitors the sensitivity of the net interest margin by utilizing income simulation models and traditional interest rate gap analysis. The Company’s balance sheet structure is primarily short-term in nature with most interest earning assets and interest bearing liabilities repricing or maturing in less than five years. The Company targets a mix of interest earning assets and interest bearing liabilities such that no more than 5% of the net interest margin will be at risk over a one-year period should short-term interest rates shift gradually up or down 2%.

     As of September 30, 2005, the Company’s income simulation model predicted net interest income would decrease $433 thousand, or 0.2%, assuming a gradual 2.0% increase in short-term market interest rates and gradual 1.0% increase in long-term interest rates. This scenario predicts the Company’s funding sources will reprice faster than its interest earning assets and at higher rates, thereby reducing interest rate spread and net interest margin. Conversely, assuming a gradual 2% decrease in short-term market interest rates and gradual 1.0% decrease in long-term interest rates, the Company’s income simulation model predicted net interest income would decrease $1.5 million, or 0.8%.

     The preceding interest rate sensitivity analysis does not represent a forecast and should not be relied upon as being indicative of expected operating results.

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LIQUIDITY MANAGEMENT

     Liquidity measures the Company’s ability to meet current and future cash flow needs as they become due. The Company manages its liquidity position to meet the daily cash flow needs of customers, while maintaining an appropriate balance between assets and liabilities to meet the return on investment objectives of its shareholders. The Company’s liquidity position is supported by management of its liquid assets and liabilities. Liquid assets include cash, interest bearing deposits in banks, federal funds sold, available-for-sale investment securities and maturing or prepaying balances in the Company’s held-to-maturity investment and loan portfolios. Liquid liabilities include core deposits, federal funds purchased, securities sold under repurchase agreements and borrowings. The Company does not engage in derivatives or related hedging activities to support its liquidity position.

     Short-term and long-term liquidity requirements of the Company are primarily to fund on-going operations, including payment of interest on deposits and debt, extensions of credit, capital expenditures and shareholder dividends. These liquidity requirements are met primarily through cash flow from operations, redeployment of prepaying and maturing balances in the Company’s loan and investment portfolios, debt obligations and customer deposits.

     For additional information regarding the Company’s operating, investing and financing cash flows, see “Consolidated Statements of Cash Flows” contained herein.

     As a holding company, FIBS is a corporation separate and apart from its bank subsidiary and, therefore, provides for its own liquidity. Substantially all of FIBS’ revenues are obtained from management fees and dividends declared and paid by its bank subsidiary. There are statutory and regulatory provisions that could limit the ability of the bank subsidiary to pay dividends to FIBS. Management of FIBS believes that such restrictions will not have an impact on the ability of FIBS to meet its ongoing cash obligations.

Item 3.

QUANTITATIVE AND QUALITATIVE DISCLOSURES
ABOUT MARKET RISK

     As of September 30, 2005, there have been no material changes in the quantitative and qualitative information about market risk provided pursuant to Item 305 of Regulation S-K as presented in the Company’s Annual Report on Form 10-K for the year ended December 31, 2004.

Item 4.

CONTROLS AND PROCEDURES

     Management of the Company is responsible for establishing and maintaining effective disclosure controls and procedures, as defined under Rules 13a-15(e) and 15d-15(e) of the Securities Exchange Act of 1934. As of September 30, 2005, an evaluation was performed, under the supervision and with the participation of management, including the Chief Executive Officer and Chief Financial Officer, of the effectiveness of the design and operation of the Company’s disclosure controls and procedures. Based on that evaluation, management concluded that the Company’s disclosure controls and procedures as of September 30, 2005 were effective in ensuring that information required to be disclosed in this Quarterly Report on Form 10-Q was recorded, processed, summarized, and reported within the time period required by the Securities and Exchange Commission’s rules and forms.

     There were no changes in the Company’s internal controls over financial reporting for the quarter ended September 30, 2005 that have materially affected, or are reasonably likely to materially affect, such controls.

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PART II.

OTHER INFORMATION

Item 1.   Legal Proceedings

     There have been no material changes in legal proceedings as described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2004.

Item 2.   Unregistered Sales of Equity Securities and Use of Proceeds

(a) During the three months ended September 30, 2005, the Company issued 500 unregistered shares of its common stock valued at $31,750 to one executive officer pursuant to the Company’s 2004 Restricted Stock Award Plan. The issuance was made in reliance upon the “no sale” provisions of Section 2(a)(3) of the Securities Act of 1933, and upon the exemption from registration (to the extent applicable) under Section 4(2) of the Securities Act of 1933.

(b) Not applicable.

(c) The following table provides information with respect to purchases made by or on behalf of the Company or any “affiliated purchasers” (as defined in Rule 10b-18(a)(3) under the Securities Exchange Act of 1934), of the Company’s common stock during the three months ended September 30, 2005.

					Total Number of	Maximum Number
					Shares Purchased	of Shares That
	Total Number				as Part of Publicly	May Yet Be
	Of Shares		Average Price		Announced Plans	Purchased Under the
Period	Purchased		Paid Per Share		Or Programs(1)	Plans or Programs
July 2005		1,985		63.50	0	Not Applicable
August 2005		2,416		65.15	0	Not Applicable
September 2005		16,819		65.50	0	Not Applicable
Total		21,220	$	65.27	0	Not Applicable

(1) The common stock of the Company is not actively traded, and there is no established trading market for the stock. There is only one class of common stock, with approximately 90.7% of the shares subject to contractual transfer restrictions set forth in shareholder agreements and approximately 9.3% without such restrictions. The Company has a right of first refusal to repurchase the restricted stock. Additionally, restricted stock held by officers, directors and employees of the Company may be called by the Company under certain conditions. The Company has no obligation to purchase restricted or unrestricted stock, but has historically purchased such stock. All purchases indicated in the table above were effected pursuant to private transactions.

     See Management’s Discussion and Analysis of Financial Condition and Results of Operations — Liquidity Management” for a discussion of working capital restrictions and other limitations on the payment of dividends.

Item 3.  Defaults upon Senior Securities

None.

Item 4.  Submission of Matters to a Vote of Security Holders

None.

Item 5.  Other Information

(a) Not applicable or required.

(b) None.

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Item 6. Exhibits

3.1(1)	Restated Articles of Incorporation dated February 27, 1986
3.2(2)	Articles of Amendment to Restated Articles of Incorporation dated September 26, 1996
3.3(2)	Articles of Amendment to Restated Articles of Incorporation dated September 26, 1996
3.4(6)	Articles of Amendment to Restated Articles of Incorporation dated October 7, 1997
3.5(17)	Restated Bylaws of First Interstate BancSystem, Inc. dated July 29, 2004
4.1(4)	Specimen of common stock certificate of First Interstate BancSystem, Inc.
4.2(1)	Shareholder’s Agreement for non-Scott family members
4.3(11)	Shareholder’s Agreement for non-Scott family members dated August 24, 2001
4.4(13)	Shareholder’s Agreement for non-Scott family members dated August 19, 2002
4.5(9)	First Interstate Stockholders’ Agreements with Scott family members dated January 11, 1999
4.6(9)	Specimen of Charity Shareholder’s Agreement with Charitable Shareholders
4.7(14)	Junior Subordinated Indenture dated March 26, 2003 entered into between First Interstate and U.S. Bank National Association, as Debenture Trustee
4.8(14)	Certificate of Trust of First Interstate Statutory Trust dated as March 11, 2003
4.10(14)	Amended and Restated Trust Declaration of First Interstate Statutory Trust
4.11(14)	Form of Capital Security Certificate of First Interstate Statutory Trust (included as an exhibit to Exhibit 4.10)
4.12(14)	Form of Common Security Certificate of First Interstate Statutory Trust (included as an exhibit to Exhibit 4.10)
4.13(14)	Guarantee Agreement between First Interstate BancSystem, Inc. and U.S. Bank National Association
10.1(18)	Credit Agreement dated June 30, 2005 between First Interstate BancSystem, Inc., as borrower, and Wells Fargo Bank, N.A.
10.2(18)	Revolving Line of Credit Note dated June 30, 2005 between First Interstate BancSystem, Inc. and Wells Fargo Bank, N.A.
10.4(2)	Note Purchase Agreement dated August 30, 1996, between First Interstate BancSystem, Inc. and the Montana Board of Investments
10.5(1)	Lease Agreement Between Billings 401 Joint Venture and First Interstate Bank Montana and addendum thereto
10.6(5)	Credit Agreement between Billings 401 Joint Venture and Colorado National Bank dated as of September 26, 1995
10.7(1)†	Stock Option and Stock Appreciation Rights Plan of First Interstate BancSystem, Inc., as amended
10.8(8)†	2001 Stock Option Plan
10.9(15)†	Employee Stock Purchase Plan of First Interstate BancSystem, Inc., as amended and restated effective April 30, 2003
10.10(3)	Trademark License Agreements between Wells Fargo & Company and First Interstate BancSystem, Inc.
10.12(10)†	Employment Agreement between First Interstate BancSystem, Inc. and Lyle R. Knight
10.13(10)†	First Interstate BancSystem, Inc. Executive Non-Qualified Deferred Compensation Plan dated November 20, 1998
10.14(7)†	First Interstate BancSystem’s Deferred Compensation Plan dated December 6, 2000
10.15(11)†	First Interstate BancSystem, Inc. 2004 Restricted Stock Award Plan
10.16(16)†	Form of First Interstate BancSystem, Inc. Restricted Stock Award Agreement
10.17(16)†	Form of First Interstate BancSystem, Inc. Restricted Stock Award — Notice of Restricted Stock Award
31.1	Certification of Quarterly Report on Form 10-Q pursuant to Section 302 of the Sarbanes Oxley Act of 2002 by Chief Executive Officer
31.2	Certification of Quarterly Report on Form 10-Q pursuant to Section 302 of the Sarbanes Oxley Act of 2002 by Chief Financial Officer
32	Certification of Quarterly Report on Form 10-Q pursuant to Section 906 of the Sarbanes Oxley Act of 2002.

†		Management contract or compensatory plan or arrangement.
(1	)	Incorporated by reference to the Registrant’s Registration Statement on Form S-1, No. 33-84540.
(2	)	Incorporated by reference to the Registrant’s Form 8-K dated October 1, 1996.
(3	)	Incorporated by reference to the Registrant’s Registration Statement on Form S-1, No. 333-25633.
(4	)	Incorporated by reference to the Registrant’s Registration Statement on Form S-1, No. 333-3250.

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(5	)	Incorporated by reference to the Post-Effective Amendment No. 2 to the Registrant’s Registration Statement on Form S-1, No. 33-84540.
(6	)	Incorporated by reference to the Registrant’s Registration Statement on Form S-1, No. 333-37847.
(7	)	Incorporated by reference to the Registrant’s Form 10-K for the fiscal year ended December 31, 2002.
(8	)	Incorporated by reference to the Registrant’s Registration Statement on Form S-8, No. 333-106495.
(9	)	Incorporated by reference to the Registrant’s Registration Statement on Form S-8, No. 333-76825.
(10	)	Incorporated by reference to the Registrant’s Form 10-K for the fiscal year ended December 31, 1999.
(11	)	Incorporated by reference to the Registrant’s Post-Effective Amendment No. 1 to Registration Statement on Form S-8, No. 333-76825.
(12	)	Incorporated by reference to the Registrant’s Form 10-K for the fiscal year ended December 31, 2000.
(13	)	Incorporated by reference to the Registrant’s Post-Effective Amendment No. 2 to Registration Statement on Form S-8, No. 333-76825.
(14	)	Incorporated by reference to the Registrant’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2003.
(15	)	Incorporated by reference to the Registrant’s Post-Effective Amendment No. 3 to Registration Statement on Form S-8, No. 333-76825.
(16	)	Incorporated by reference to Registrant’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2004.
(17	)	Incorporated by reference to Registrant’s Post-Effective Amendment No. 4 to Registration Statement of Form S-8, No. 333-76825.
(18	)	Incorporated by reference to the Registrant’s Form 8-K dated June 30, 2005.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

	FIRST INTERSTATE BANCSYSTEM, INC.
Date October 24, 2005	/s/ LYLE R. KNIGHT
	Lyle R. Knight
	President and Chief Executive Officer
Date October 24, 2005	/s/ TERRILL R. MOORE
	Terrill R. Moore
	Executive Vice President and
	Chief Financial Officer

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