DALLAS, TEXAS, February 11, 1999 -- Allegiance Telecom, Inc. (Nasdaq: ALGX) announced today that Mark B. Tresnowski, has joined the Company as senior vice president and general counsel. He is based in Westchester, Illinois.

Prior to joining Allegiance, Tresnowski, 39, served as a partner in the corporate, securities and venture capital practices at Kirkland & Ellis in Chicago. While at Kirkland & Ellis he represented Allegiance in the Company's initial public offering of common stock as well as in its two high-yield debt offerings. He has developed a broad base of transactional law expertise while representing clients ranging from emerging growth companies to Fortune 100 companies, such as Ameritech Corporation and Motorola, Inc., on domestic and international debt and equity financings, mergers and acquisitions and joint ventures.

"Mark is highly regarded in the legal arena and brings a wealth of experience in securities law and mergers and acquisitions to our Company," said Royce Holland, chairman and CEO of Allegiance Telecom. "Having represented us over the past year and a half, we have benefited immensely from his advice and counsel and are delighted that he has decided to become a full-time member of our team."

Tresnowski graduated from The University of Virginia School of Law, where he received a J.D. in 1986 and served as editor of the Virginia Law Review from 1984 to 1986. He earned his B.A. degree from The University of Illinois in 1982--that same year he became a Certified Public Accountant. Tresnowski resides in Inverness, Illinois.

Allegiance is a competitive local exchange carrier (CLEC) based in Dallas, Texas. The Company offers businesses a complete package of telecommunications services, including local, long distance, international calling, high-speed data transmission and Internet services. Allegiance is targeting 24 major metropolitan areas in the U.S. with its "one-stop shopping" approach. Allegiance currently provides service to the Atlanta, Boston, Chicago, Dallas, Fort Worth, Los Angeles, New York, Philadelphia, Oakland and San Francisco markets. The Company's web address is: www.allegiancetele.com.