Doctors in San Francisco, testifying that marijuana has medical benefits, said they permit cancer patients undergoing chemotherapy to smoke the drug for therapeutic reasons.

Appearing last week at a court-ordered hearing on the proposed legalization of marijuana for medical purposes, Dr. Ivan Silverberg of the University of California at San Francisco said, "To be honest, I do not even think of marijuana as being illegal.

"This in-hospital use, which takes place in rooms behind closed doors, is . . . welcomed by nurses, said Silverberg. "Instead of having to run back and forth with buckets of vomit, they are allowed to treat patients who are more well-controlled than they would be without marijuana."

Dr. Ernest Rosenbaum of Mount Zion Hospital said, "Marijuana makes most cancer patients more comfortable {during} chemotherapy. So we tacitly encourage it."

The drug is used to control the nausea caused by chemotherapy. Its active ingredient is also available in a legal pill form, but many patients find the smoke more effective. It is also an appetite stimulant, said Dr. Tod H. Mikuriya, an authority on psychoactive drugs.

Last Tuesday's hearing was the first of several to be conducted in San Francisco and Washington by an administrative judge of the Drug Enforcement Administration, which has resisted moves to permit doctors to write marijuana prescriptions.