(FORTUNE Magazine) – Health maintenance organizations might seem like big winners if Hillary Rodham Clinton's health care program emphasizes so-called managed competition. But murmurs from Washington of federal price controls have dampened HMOs' high expectations. Worried investors sent share prices of the two largest publicly owned HMO operators tumbling in February, and they haven't recovered. Grumbles United Healthcare CEO Bill McGuire: ''Price controls have never resulted in a favorable impact.'' Left alone, HMOs hold costs down, one reason some 40 million Americans are members, with their employers often footing the bill. According to a survey of U.S. employers by the Foster Higgins benefits consulting firm, HMO costs rose 8.8% in 1992, vs. a 14.2% rise for traditional fee-for-service plans. A managed-care approach from Washington would push more employees into HMOs, which large employers would like to pit against each other to lower costs. But HMOs often prefer to compete on service rather than price. And Foster Higgins principal John Erb notes that an 8.8% cost increase, while better than traditional plans', is still three times 1992 inflation. Most experts say that savings from managed competition will very likely be slow in coming. That leaves price controls looking like a seductive quick fix for a President who needs results. Says Erb: ''President Clinton has to come back in 1996 with Ross Perot-like charts that show two things. One, that he's increased access to health care. Two, that he's controlled costs. So the political pressure to impose price controls is intense.'' That's what HMOs fear most. Many health care experts, recalling President Nixon's failed price controls in the early 1970s, sneer at such efforts. As Kenneth Abramowitz, a health care industry analyst at Sanford Bernstein, points out: ''Price controls have never worked in any society. The last one they destroyed was called the Soviet Union.''

CHART: NOT AVAILABLE CREDIT: FORTUNE CHART/SOURCE: SANFORD BERNSTEIN CAPTION: MORE AMERICANS ENROLL IN HMOs. . . BUT STOCKS AIL