Arbinet-thexchange, Inc. Prices Initial Public Offering at $17.50 Per Share

New Brunswick, NJ - December 16, 2004 - Arbinet-thexchange, Inc. (NASDAQ: ARBX) announced today that its initial public offering of 6,535,405 shares of common stock, 4,233,849 shares of which are being sold by Arbinet and 2,301,556 shares of which are being sold by certain stockholders of Arbinet, has been priced at $17.50 per share. Certain stockholders of Arbinet have also granted the underwriters a 30-day option to purchase up to 980,310 additional shares to cover over-allotments, if any.

The underwriters for the offering are led by Merrill Lynch & Co., acting as sole book-running manager, Lehman Brothers acting as the joint lead manager, with SG Cowen & Co., William Blair & Company and Advanced Equities, Inc., acting as co-managers.

A copy of the final prospectus relating to the offering may be obtained by contacting: Merrill Lynch & Co., Prospectus Department, 4 World Financial Center, New York, NY 10080; or 212-449-1000.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

About Arbinet

Arbinet is the leading electronic market for trading, routing and settling communications capacity. Members of the exchange, consisting primarily of communications service providers, anonymously buy and sell voice calls and Internet capacity based on route quality and price through its centralized, efficient and liquid marketplace. Members place orders through a web-based interface. Its fully automated, highly scalable trading platform matches these orders using proprietary software and delivers them through state-of-the-art facilities.

Contact:

Chris Reid: 732.509.9160 - creid@arbinet.com