Fred Bartley (Bart) Jepson, 50, a Montgomery County science teacher, died of cancer Thursday at Georgetown University Hospital. He had been an out-patient in a national research program conducted at the Vincent T. Lombardi Cancer Research Center at the hospital.

Mr. Jepson, who had a bachelor's degree in chemistry and a master's degree in education from American University, was head of the department of science of Julius West Junior High School in Rockville until September, when he left because of illness. Prior to that he had been a science teacher in White Oak, at Springbrook High School and Francis Scott Key Junior High.

Born in Titusville, Fla., Mr. Jepson came to Washington in the 1930s and graduated from Western High School. He served two years in the Navy before attending American University.

He was a member of the Silver Spring Junior Chamber of Commerce and the Kiwanis Club. He also served as president of the White Oak Men's Major Bowling League.

Suvivors include his wife. Joy: a daughter, Christina: two sons, Lawrence Peter and Walter Rollin, all of the home in Silver Spring: his parents, Mr. and Mrs. Fred W. Jepson of Silver Spring, and two brothers, William Terry of Crofton and Lawrence, currently residing in Europe.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society.