Alan Rothenberg, 39, a Washington lawyer who specialized in tax legislation and who helped a Romanian couple get their daughter to this country, died of pneumonia Tuesday at George Washington University Hospital.

Mr. Rothenberg was a partner in the Washington office of the Los Angeles-based law firm of Paul, Hastings, Janofsky & Walker. A former tax counsel for the Republican minority of the House Ways and Means Committee, he helped persuade Congress to liberalize tax treatment of Americans living abroad to allow U.S. companies to compete more easily with foreign firms.

He also helped persuade the Romanian government to allow the daughter of Bela and Marta Karoly, the coach and assistant coach of the Romanian gymnastics team, to join her parents in the United States. The Karolys defected here last year.

At the time of his death, Mr. Rothenberg was engaged in efforts to persuade the Romanians to allow the wife and daughter of Gheza Pozsar, the head choreographer of the Romanian team, to leave their country.

Mr. Rothenberg, who was born in Baltimore, earned bachelor's and law degrees at the University of Maryland. He worked for the old Atomic Energy Commission and then joined the staff of the late Rep. William Steiger (R-Wis.). In 1978, he transferred to the staff of the House Ways and Means Committee. He joined Paul, Hastings, Janofsky & Walker in 1980.

He was a member of the D.C., Maryland and Federal bar associations.

Mr. Rothenberg, who lived in Chevy Chase, is survived by his wife, Patricia, and two children, Alison and Andrew, all of Chevy Chase; his parents, Jack and Selma Rothenberg of Baltimore, and a sister, Susan Erickson of Annapolis.

The family suggests that expressions of sympathy be in the form of contributions to the Jewish National Fund, 2025 I St. NW, Suite 808, Washington, D.C., 20006.