The Rev. Clarence Marcellus Long Jr., 60, pastor of Mount Airy Baptist Church in Washington since 1956, died of cancer Monday at Howard University Hospital.

During his tenure, the church built and for some years operated a low and moderate-income family apartment project, Tyler House. It is located on North Capitol Street near the church.

The C. M. Long Jr. Church Extension Center also was built to serve both the church at 17 St. NW and the community.

Dr. Long was born in Charlottesville, the son of a Baptist minister, the Rev. Dr. Clarence M. Long. He grew up in Norfolk and East Orange, N.J. He was among the first graduates of the School of Journalism at Lincoln University in Jefferson City, Mo., and worked as a copy editor for a year at the Baltimore Afro-American.

Dr. Long then turned to the ministry and entered the Graduate School of Theology at Oberlin College in Ohio. He was ordained a Baptist minister in New Rochelle, N.Y., where he served as an assistant to his father, who was pastor of Bethesda Baptist Church there.

After a term as pastor of Bethlehem Baptist Church in McKeesport, Pa., and earning a master's degree in religious education from the University of Pittsburgh, Dr. Long rejoined his father in 1950 as copastor of Bethesda Baptist Church. He remained there until coming to Mount Airy in Washington.

In 1972, Dr. Long received an honorary doctor of divinity degree from the Virginia Seminary at Lynchburg.

He was active in the Baptist Ministers Conference, the Sunday School and Baptist Training Union Congress in Washington, and the Protestant Ministers Association, the Interdenominational Ministers Alliance and the National Baptist Convention, U.S. A., Inc.

Dr. Long had been a delegate to the White House Conference on Aging. He belonged to the NAACP and the Masons.

He is survived by his wife, Laverne S., of the home in Washington: two daughters, Cheryl M., and Patricia L. Tucker, and a son, Clarence M. Ill. all of Washington; his mother, Maude S. Long, and a sister, Naomi L. Andrews, both of Detroit; a brother, Wilbur F., of New Rochelle, and one grandchild.