Franklin R. Bruns Jr., 66, an official of the Smithsonian Institution who wrote a nationally syndicated stamp column died of cancer Saturday at the Washington Adventist Hospital.

Mr. Bruns came to Washington in 1951 and worked for six years as curator of the Smithsonian's philatelic collection.

He worked as director of the old Post Office Deparmtne division of philately, and chaired the Citizen's Stamp Advisory Committee, before returning to the Smithsonian as a reserarch associate in 1972. He was named supervisor and curator of the Smithsonian's division of postal history in 1977.

His column began appearing in The Post in 1953. He also was the Washington correspondent for Linn's Stamp News, and wrote a number of books on stamp and coin collecting. He contributed articles to the Ncylopedia Brittanica's Collier's yearbooks.

He was appointed to the Treasury Department's assay commission in 1973.

Mr. Bruns served as president of the American Philatelic Congress from 1944 to 1947, and later edited the organization's official publication, "The Congress Books," for a time during the 1950s. He received a special service award from the Congress in 1966.

He was a director of the Society of Philatelic Americans and the American Academy of Philately. He also was an honorary life member of the American Air Mail Club of Washington.

Mr. Bruns was a native of New York City. He started collecting stamps at the age of 9, and writing about them for the New York Sun while attending New York University. He was philatelic editor of The Sun and the New York World-Telegram and Sun from 1932 until coming to Washington in 1951.

He received a number of awards for his writing, including the Barry Bowl Prize, in each of the best newspaper stamp column, and the Philatelic Journalists of America award for the best newspaper stamp column.

Mr. Bruns was a resident of Takoma Park.

He is survived by two daughters, Pricilla Lee Sando, of Greenbelt, and Katharine A. Kerdock, of Takoma Park; two sons, Franklin R. III, of Colesville, and James H., of Berwyn Heights, and eight grandchildren.