Martin Fishbein, 73, of Center City, an influential social psychologist who was active with AIDS prevention, died of a heart attack Nov. 27 at Royal Free Hampstead Hospital in London.

Dr. Fishbein was director of the health communication program in the Public Policy Center of the Annenberg School for Communication at the University of Pennsylvania.

Dr. Fishbein, who had been at Penn since 1997, studied the role of attitudes and social norms to understand why people engage in certain behaviors. He was the author of seven books and contributed more than 250 articles and chapters to professional books and journals.

"Marty was an academic star, but he was a man also of great loyalty to his friends, to his colleagues, to his students. He was always trying to find opportunities for them to succeed," said Robert Hornik, a colleague at the Annenberg School.

Another colleague, Michael Hennessy, said he was impressed when Dr. Fishbein told him, "I try to find people who are smarter than I am so I can hire them." Hennessy said, "In my experience, academics avoid or actively discourage people who are perceived as smarter than them."

In 1975, while on the faculty of the University of Illinois, Dr. Fishbein coauthored an important book with Icek Ajzen, Belief, Attitude, Intention and Behavior. In the late 1980s, he was a consultant to the National Institute of Mental Health on the AIDS epidemic, and from 1992 to 1996 he was a guest AIDS researcher at the Centers for Disease Control and Prevention in Atlanta. He helped develop programs for the CDC to encourage safer behavior, such as using condoms, to prevent AIDS.

Dr. Fishbein was an organizer of the International Impact AIDS conferences sponsored by the Human Sciences Research Council. He had participated in the ninth-annual conference in September in Botswana and had gone to London last month to attend an Impact AIDS board meeting to plan the 10th-annual conference next year in New Mexico.

A native of Jamaica, N.Y., Dr. Fishbein earned a bachelor's degree from Reed College in Portland, Ore. He joined the University of Illinois faculty in 1961 after earning a doctorate in psychology from the University of California, Los Angeles. He and his wife, Debbie, met in California and married in 1959.

They enjoyed opera and theater and dance programs at the Annenberg Center for Performing Arts, and collecting native folk paintings, sculpture, and assemblages.

"Marty was tremendously successful as a theorist and researcher," Hornik said, "but he appreciated so much else as well - a good meal, a good beer, a new play, and the personal relationships he built each place he went."

In addition to his wife, Dr. Fishbein is survived by a sister, Toby Murray; and two nephews.

A memorial service will be held Feb. 18 at the Annenberg School for Communication at the University of Pennsylvania.