A lack of money and the complexities of the medical business have claimed another one of the nation's doctor-owned managed-care companies, this time in California.

California Advantage, started by the California Medical Association and 7,500 of its member physicians, filed for bankruptcy Wednesday. The privately held company will liquidate gradually, allowing it to cover existing policies.California Advantage, based in Oakland, lost $11 million as it failed to sign up enough patients and investors, the company said. A lack of money was the primary problem, said Steven Fleisher, a lawyer for the association.

"We undertook a much larger (task) than we could realistically do with the amount of capital we had," he said.

California Advantage sought Chapter 11 protection in U.S. Bankruptcy Court in Oakland, but the company will liquidate, Fleisher said.

The company's fate is a frequent one among concerns formed in recent years by doctors hoping to avoid giving up fees and control of patient care to HMOs, industry analysts said.

"They either go bankrupt . . . or never make money," said Kenneth Abramowitz of Sanford C. Bernstein & Co. in New York. "No one's forming them any more, and the ones that have formed are, by and large, selling out."

California Advantage was started in January 1996 by the CMA and doctors who invested $1,000 each.

Managers said last year they hoped to sign up 3.3 million people - 10 percent of California's population - within a decade. But the company attracted only 6,000 subscribers, far below the 40,000 it said it needed to break even.

California Advantage also said it tended to draw subscribers who were somewhat sicker - and costlier to treat - than average because it offered partial payment for out-of-network doctors, including specialists.

The company also had trouble attracting physicians to invest in the venture. Many of CMA's member doctors work for competing HMOs. Companies also balked because CMA did not want to sell a majority interest in the plan, giving up physician control.