John L. (Jack) Hagerty, 78, the athletic director of Georgetown University for 20 years before retiring in 1969 and the school's varsity football coach for 16 years before that, died March 23 at Georgetown University Hospital after a heart attack. He lived in Washington.

Mr. Hagerty's record as football coach included 23 consecutive victories from 1938 to 1940. The string broke when Boston College defeated the Hoyas, 19-18, in a contest that the famed sportswriter Grantland Rice called the greatest football game he ever saw. At the end of the 1940 season, Georgetown went to the Orange Bowl and lost 14-7 to Mississippi State University.

This was the beginning of the end for major intercollegiate football at Georgetown. In a 1966 story in The Hoya, the Georgetown University student newspaper, Mr. Hagerty maintained that only about 50 schools really had the will and the facilities to compete at the top level. He maintained that he had believed since the early 1950s that football at Georgetown "should be considered a student activity just like a newspaper or yearbook."

Mr. Hagerty was a native of Dorchester, Mass. After he entered Georgetown's School of Foreign Service, he gained fame as a baseball centerfielder. He was the chief running threat on the football team from 1923 through 1925 and the team captain in 1925.

After leaving school, Mr. Hagerty spent several years with the New York Giants football team as a quarterback and punt-returner. He was an assistant football coach at Holy Cross for a year before returning to Georgetown in 1932 as its head football coach.

The Rev. Timothy S. Healy, S.J., the president of Georgetown, said Mr. Hagerty's "successes on the gridiron in his day set the tone for Georgetown's athletic program today."

Mr. Hagerty's survivors include his wife, Agnes K., of Washington; a daughter, Barbara H. Cosentino of Dover, Mass., and six grandchildren.