SEC FORM 3

SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person^*

Eng Chi K

(Last)

(First)

(Middle)

C/O ARBINET-THEXCHANGE, INC

120 ALBANY STREET, TOWER II, SUITE 450

(Street)

NEW BRUNSWICK

08901

(City)

(State)

(Zip)

2. Date of Event Requiring Statement (Month/Day/Year)
12/15/2004

3. Issuer Name and Ticker or Trading Symbol
ARBINET THEXCHANGE INC [ ARBX ]

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director	10% Owner
X	Officer (give title below)	Other (specify below)
	General Counsel and Secretary

5. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock	10,265⁽¹⁾⁽¹⁰⁾	D

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
Stock Option (right to buy)	03/01/2001⁽²⁾	02/28/2005	Common Stock	3,750⁽³⁾	$2.03⁽³⁾	D
Stock Option (right to buy)	03/01/2001⁽⁴⁾	12/04/2011	Common Stock	1,250⁽⁵⁾	$0.16⁽⁵⁾	D
Stock Option (right to buy)	08/03/2002⁽⁶⁾	08/02/2011	Common Stock	3,125⁽⁵⁾	$0.16⁽⁵⁾	D
Stock Option (right to buy)	06/14/2003⁽⁷⁾	06/13/2012	Common Stock	28,125⁽⁵⁾	$0.16⁽⁵⁾	D
Stock Option (right to buy)	06/14/2002⁽⁸⁾	06/13/2012	Common Stock	62⁽⁵⁾	$0.16⁽⁵⁾	D
Stock Option (right to buy)	01/08/2005⁽⁹⁾	01/07/2014	Common Stock	3,421⁽⁵⁾	$8.32⁽⁵⁾	D
Stock Option (right to buy)	12/10/2004⁽¹¹⁾	11/09/2014	Common Stock	25,000⁽⁵⁾	$15.04⁽⁵⁾	D

Explanation of Responses:

1. Restricted common stock, a portion of which remains subject to repurchase by the Issuer.

2. This stock option vests as to 25% of the shares on each anniversary of the grant date beginning March 2, 2001.

3. (a) Reflects a 2-for-1 forward stock split, which became effective March 8, 2000, pursuant to which (i) the number of shares of common stock was multiplied by 2 and (ii) the exercise price of this option was divided by 2, and (b) Reflects a 1-for-16 reverse stock split, which became effective on November 30, 2004, pursuant to which (i) the number of shares of common stock was divided by 16 and (ii) the exercise price of this option was multiplied by 16.

4. This stock option vests as to 25% of the shares on March 1, 2001 and as to 1/48th of the remaining shares monthly over a 36-month period beginning December 5, 2001.

5. Reflects a 1-for-16 reverse stock split, which became effective on November 30, 2004, pursuant to which (i) the number of shares of common stock was divided by 16 and (ii) the exercise price of this option was multiplied by 16.

6. This stock option vested as to 25% of the shares on August 3, 2002 and as to 1/48th of the remaining shares monthly over the 36-month period thereafter.

7. This stock option vested as to 25% of the shares on June 14, 2003 and as to 1/48th of the remaining shares monthly over the 36-month period thereafter.

8. This stock option is fully vested.

9. This stock option vested as to 25% of the shares on January 8, 2005 and as to 1/48th of the remaining shares monthly over the 36-month period thereafter.

10. Reflects a 1-for-16 reverse stock split, which became effective on November 30, 2004, pursuant to which the number of shares of common stock was divided by 16.

11. This stock option vests monthly over a 36-month period which began December 10, 2004.

	/s/ Chi K. Eng	12/15/2004
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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