Consolidated Statements of Cash Flows (USD $) In Thousands	12 Months Ended
	May 31, 2011		May 31, 2010		May 31, 2009
OPERATING ACTIVITIES:
Net income	$ 89,327		$ 82,583		$ 76,183	[1]
Depreciation and amortization	18,213		16,569		13,306
Loss on retirement of fixed assets	1,072		538		352
Provision for doubtful accounts	371		361		848
Share-based compensation expense	6,941		5,946		5,904
Deferred income taxes	941		4,994		5
Excess tax (benefits) shortfall from share-based compensation	(1,792)		183		(3,253)
Accrued refund of BioArray escrowed funds	(4,256)	[2]		[2]		[2]
Changes in operating assets and liabilities:
Accounts receivable, trade	757		(6,386)		(6,310)
Income taxes	(2,790)		1,037		7,796
Inventories	(8,248)		(12,551)		(4,647)
Other assets	875		(102)		(7,450)
Accounts payable	2,412		(1,060)		796
Deferred revenue	(3,595)		(5,258)		(2,247)
Accrued expenses and other liabilities	1,883		(2,103)		(1,461)
Cash provided by operating activities	102,111		84,751		79,822
INVESTING ACTIVITIES:
Purchases of property and equipment	(9,061)		(6,304)		(8,602)
Acquisition of businesses, net of cash acquired					(107,954)
Cash used in investing activities	(9,061)		(6,304)		(116,556)
FINANCING ACTIVITIES:
Repayments of long-term debt and capital leases					(206)
Repurchase of common stock	(526)		(11,910)		(7,621)
Proceeds from exercise of stock options	1,312		336		3,178
Excess tax benefits (shortfall) from share-based compensation	1,792		(183)		3,253
Cash provided by (used in) financing activities	2,578		(11,757)		(1,396)
EFFECT OF EXCHANGE RATES ON CASH AND CASH EQUIVALENTS	4,326		(502)		(465)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	99,954		66,188		(38,595)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	202,649		136,461		175,056
CASH AND CASH EQUIVALENTS AT END OF YEAR	302,603		202,649		136,461
SUPPLEMENTAL INFORMATION:
Tax paid	43,090		36,295		32,528
Interest paid					36
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Accrued refund of BioArray escrowed funds	2,935	[2]		[2]		[2]
Movement from inventory to property and equipment for instruments placed on rental agreements	12,857		13,733		6,707
Shares surrendered for amounts due on stock options exercised					$ 516

[1] Certain numbers have been reclassed to conform to current year presentation.

[2] In fiscal 2011, the Company accrued the release of escrowed funds related to the acquisition of BioArray. In accordance with the contingent consideration guidance in ASC 805 "Business Combinations," $2.9 million of the $7.2 million returned to the Company was recorded to Goodwill as it relates to items that were predefined as contingent items in the Merger Agreement and are considered measurement period adjustments. The $2.9 million appears in the Non-cash Investing and Financing Activities on the Consolidated Statement of Cash Flows. The remaining $4.3 million was recorded to Other Income as it is not considered a measurement period adjustment and appears as an adjustment to net income in the operating activities of the Consolidated Statement of Cash Flows.