Dr. Vilenchik, who defected from the Soviet Union, had been on the staff of the Longevity Achievement Foundation at the Sally Balin Medical Center in Media since 1995. The center specializes in dermatology, cosmetic surgery and longevity medicine.

Dr. Arthur K. Balin, the center's founder, described Dr. Vilenchik as an internationally recognized scientist who made significant contributions to the fields of aging and radiation biology. "He was a pure scholar and a true gentleman," Balin said.

As early as the 1970s, in his native Russia, Dr. Vilenchik was doing groundbreaking research.

He studied the crucial role that repair to DNA damage can have on human protection against cancer and degenerative diseases.

In addition to his work at the Longevity Achievement Foundation, Dr. Vilenchik collaborated with Dr. Alfred Knudsen, a prominent medical researcher at the Fox Chase Cancer Center.

The men studied the genetic effects of radiation and published three scientific papers on the subject. They were preparing to publish a fourth. "His mind was fixed on his work even after he became ill," Dr. Knudsen said.

Dr. Vilenchik earned a medical degree in Russia and earned a doctoral degree in biophysics from the Presidium of the Academy of Science of the USSR.

He was a senior scientist at the Institute of Biological Physics of the USSR Academy of Sciences in 1990 when he was invited to lecture at the Medical Research Council in Harwell, England.

While in England he defected from the Soviet Union and moved to Israel, where he was an associate with the Institute for Environmental Research at Tel Aviv University for a year.

From 1991 until 1995, he was a research scientist at the State University of New York Health Science Center in Syracuse and at Cornell University.

Dr. Vilenchik is survived by a daughter, Janna Volkova; and a sister, Anna Kokotova.

No services are planned.