Leland P. Bradford, 75, an internationally known educator and retired director of the National Education Association's National Training Laboratories (NTL) Institute who also wrote on the problems of retirement, died of a massive heart rupture Wednesday at a hospital in Pinehurst, N.C.

In 1947, Dr. Bradford was named director of the NEA's National Training Laboratory in Group Development, a pioneering venture in research and training in the process of group thinking and group dcision-making. Located in Arlington, it is now known as the NTL Institute for Applied Behavioral Science and is considered to be this country's leading professional institute for experience-based group methods.

Dr. Bradford served as director for 25 years before retiring in 1972.

Born in Chicago on July 12, 1905, he earned bachelor's, master's and doctor's degrees from the University of Illinois. While a doctoral student, he served as State Director of the Adult Education for the Works Progress Administration (WPA) in Illinois.

During World War II, he moved to Washington as chief of training for the U.S. Immigration and Naturalization Service and later held the same psoition at the Federal Security Agency.

In 1945, the NEA named him first executive secretary of their then-new Department of Adult Education and director of the Division of Adult Education Services.

Dr. Bradford later served as secretary of the International Committee on Adult Educaton of the World Confederation of Organizations of the Teaching Profession (WCOTP). He also was a delegate to many postwar international conferences, including the first United Nations Conference on the Elimination of Prejudice.

In the mid-1950s, he served as a consultant to the European Productivity Agency in Paris.

Dr. bradford coedited what is considered to be the definitive work in the field of behavioral science, "T-Group Theory and Laboratory Method: Innovation in Reeducation," published in 1964. He wrote or edited six books and more than 150 articles.

After retiring, he and his wife, the former Martha De Maeyer, wrote "Retirement: Coping with Emotional Upheavals," published in 1979, and articles and periodicals on the subject of retirement.

Dr. Bradford, who lived in Pinehurst, was a member of numerous professional organizations and a Fellow of the National Training Laboratories and the American Psychological Association.

Besides his wife, survivor include a son, Dr. David Lee Bradford of Stanford University, and two grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the Heart Fund of the American Heart Association or to Moore Memorial Hospital in Pinehurst.