John K. Tabor, 78, a former Commerce Department undersecretary who also practiced governmental affairs and corporate law with Washington firms and on his own, died Sept. 6 at the Woodbine Rehabilitation & Healthcare Center after a stroke.

Mr. Tabor had been prominent in Pennsylvania Republican politics when President Richard M. Nixon appointed him undersecretary of commerce in 1973. In the following two years, Mr. Tabor was active in the department's effort to increase American exports and promote minority business enterprises.

In 1975, he joined the Washington firm of Purcell & Nelson, which later became Reavis & McGrath. He also taught a course on developments in corporate law at George Mason University and served on the American Bar Association committee on corporate laws.

After retiring in 1980, he wrote a biography of his father, Edward O. Tabor, who was a lawyer active in Pittsburgh civic affairs.

The younger Mr. Tabor, a District resident, was born in Uniontown, Pa., and raised in Pittsburgh. He graduated from Yale University in 1943 and served in the Naval Reserve during World War II.

After the war, he received a master's degree in history from Cambridge University and a law degree from Harvard University. He then worked for law firms in New York City and Pittsburgh and served as Pennsylvania's secretary of commerce.

He was a member of the vestry of St. John's Episcopal Church in Washington and of the Metropolitan Club.

Survivors include his wife of 47 years, Kate Williams Tabor of Washington; two sons, John K. Tabor Jr. of Portsmouth, N.H., and William H. Tabor of Alexandria; and three grandchildren.