Boyd Janney Brown, 79, a former lieutenant governor of the Virgin Islands and a retired Defense Department aide, died Sunday at Georgetown University Hospital.

A certified public accountant, he joined the Department of the Army in 1952, and after several years moved into the office of the comptroller of the Defense Department.

There Mr. Brown helped to establish a new system of bookkeeping under which the department could determine the specific cost of each item produced at its arsenals. Until then, there had been only a general accounting of such overall production costs.

Mr. Brown retired in 1972. Since then he had devoted his time between his home in Washington and a farm in Lincoln Va., known as Circleville Farms.

Born in Washington, Mr. Brown was a graduate os Swarthmore College.

He served as lieutenant governor of the Virgin Islands in 1931-34. He then became the fndiserp o tirts-Virhtef became the first president of the Virgin Islands Co., established in St. Croix to run sugar mills.

He returned to the United States in about 1940 and became secretary-treasurer of W. A. Taylor and Co., importers of liquors in New York.

In 1949, Mr. Brown moved to Taneytown, Md., where he was an official of the Sanitary Products Corp., a notions firm. He came to Washington in 1952.

Mr. Brown was a member of the Florida Avenue Friends Meeting.

He is survived by his wife, Isabel Dean Short Brown Harvey, os Swarthmore, Pa.; two sons, Miles, of Annandale, and Edward, of Lincoln, Va.; two sisters, Mrs. James W. Roberts of Norfolk, and Mrs. Robert B. Greer, of Swarthmore; a brother, Dr. Thomas McPherson Brown, of Arlington, and four grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the American Friends Service Committee in Philadelphia.