Dr. Baruj Benacerraf, Fabyan Professor of Comparative Pathology at the Medical School, plans to donate his $72,000 share of the 1980 Nobel Prize for medicine and physiology to Harvard's Sidney Farber Cancer Institute, which he heads.

"As president [of the Farber Institute] I could think of on better way to use the money," Benacerraf said yesterday. He added that the Farber Institute will soon start a $20-30 million fund drive, and that he hopes his gift will encourage other donors.

Richard A. Smith '46, chairman of the Farber Institute from 1979 until this month, said the fund drive was now in the planning stage and would begin in "two to three years." Smith, who was replaced by M. Dozier Gardner, announced Benacerraf's gift at the institute's annual meeting Tuesday.

Benacerraf shared the Nobel Prize for Medicine in 1980 with George Snell of the Jackson Laboratory in Bar Harbor, Maine, and Jean Dausset of the University of Paris. He received the award for his work on genetics and the immune system, which protects animals against dangerous substances.

The money given by Benacerraf will help provide training and research opportunities for young scientists at the Farber Institute Benacerraf has expressed concern over the decline in such opportunities and its effect on the future of American science.

Dr. Emil R. Unanue, Mallinkrodt Professor of Immunopathology, said yesterday that though Nobel Prizes are intended to support the recipients' own work, prize winners occasionally donate the money to institutions.

The Farber Institute conducts research to understand basic principles of immunology and genetics which may lead to new cancer treatments as well as trying to cure cancer victims by conventional means.

Gardner said yesterday that Benacerraf's gift "reveals the intensity of his commitment and the quality of his leadedrship.