Colleagues remember him as witty and charming, a crisp professional with a confident bedside manner, a flair for storytelling and a generosity of spirit that led him on risky overseas trips to provide free medical care for the poor.

Gerald Barnes, who held the post of chief physician at a prominent health clinic here, seemed to many the very embodiment of Hippocratic virtues. But he is not a doctor and has never attended a medical school, the authorities say, adding that, in fact, his only formal training in a health-related field is a bachelor's degree in pharmacology.

On Monday, Mr. Barnes, 62, was charged in Federal court with, among other crimes, fraud and practicing medicine without a license at the Executive Health Group, a downtown Los Angeles medical center specializing in preventive care and annual physicals, where he has worked since July 1995.

But he has long been masquerading as a doctor. In the late 1970's, according to court documents, after he legally changed his name from Gerald Barnbaum, he began impersonating an orthopedic surgeon from Stockton, Calif., named Gerald Barnes. And as Dr. Barnes, he embarked upon a career that was halted in 1981 with his guilty plea to involuntary manslaughter and practicing medicine without a license. He was sentenced to three years in a California prison and after serving 18 months, was released on parole in 1983. But then, the authorities say, he picked up where he had left off. Behind his smooth mask, they say, is a prodigiously talented con artist.