THE REV. JAMES J. KORTENDICK, 79, former head of the department of library science at Catholic University and a leader in library associations, died of cancer July 14 at the St. Martin's Home in Catonsville, Md., where he had been serving as part-time chaplain since 1978.

Father Kortendick, a member of the Society of St. Sulpice, was head of Catholic University's department of library science from 1946 until he retired in 1972. He joined the university staff as assistant librarian in 1941.

He was a former president of the library education division of the American Library Association and chairman of the association's organization and management development committee. He also had served as president and chairman of the research committee of the Association of American Library Schools and had twice been president of the D.C. Library Association. For 10 years he was chairman of the Catholic periodical index committee of the Catholic Library Association.

Born in Pecatonica, Ill., Father Kortendick graduated from St. Mary's Seminary in Baltimore, did graduate study in library science at Catholic University where he also earned master's and doctoral degrees in education.

He was a professor of English and religion at St. Edward's Seminary in Seattle during the 1930s and was instrumental in the founding of Serra International, an organization that promotes vocations in the priesthood and religious life. He was ordained in 1934.

After his retirement from Catholic University, Father Kortendick was interim library director at Marquette University in Milwaukee.

Survivors include three sisters, Marion Lawton of Milwaukee, Sister Madelyn Kortendick, a Dominican nun, of Bloomington, Ill., and Sister Marie Laurence Kortendick, also a Dominican nun, of Sinsinowa, Wis.