(MONEY Magazine) – Until recently, consumers trying to choose among health maintenance organizations (HMOs) had to settle for word-of-mouth recommendations or mount a painstaking investigation of their own. But now help is on the way: A five-year-old accrediting organization called the National Committee for Quality Assurance (NCQA) is rating a growing number of HMOs on the caliber of their medical treatment, physicians' qualifications, preventive health services, medical record keeping, appropriateness of care, and patients' rights. So far, NCQA's teams--two to three physicians plus a quality-management consultant--have reviewed roughly a third of the nation's 574 HMOs, which account for nearly 50% of all HMO enrollees. Within the next few months, NCQA will issue evaluations on another 33 HMOs; 120 more are scheduled.

The NCQA is funded by corporate purchasing groups, the HMO industry and research groups, and its evaluations are now paid for by participating HMOs (average cost: $40,000); they are entirely voluntary. But that doesn't guarantee them a good grade. Roughly one of every eight HMOs tested has failed, including Aetna Health Plans of San Diego and Humana Health Care Plan of South Florida. Another 52% have rated only one-year or partial accreditation, rather than the full three-year approval, because of lackluster performance in a few areas.

To learn how your HMO fared in a review or whether one is planned, call NCQA at 202-955-3515 and request its free Accreditation Status List. If your HMO was reviewed, the list will tell you whether it was accredited for three years, one year, provisionally or failed altogether (but not how it fell short). The list also mentions which HMOs have evaluations scheduled.

Obviously, you can rest easy if an HMO you're investigating received top honors. What if it got just provisional accreditation, as is the case for MetLife HealthCare Network of California in Long Beach? For now, be sure to consider your other health-plan choices. Then, check back in a year to see whether the HMO improved enough to earn full accreditation. Also, by next spring, the NCQA will begin offering "summary reports" that explain how each HMO stacks up against the averages.

Although a poorly run HMO is likely to duck any NCQA review, don't assume that's the only reason a plan doesn't request one. Health-group execs may find the price tag too stiff. Or if the HMO already has a reputation for quality, it may opt to skip the rating. Consumer advocate Charles Inlander, president of the People's Medical Society in Allentown, Pa., notes that in the changing health-care marketplace, eventually all HMOs will submit to evaluation, since they'll need NCQA accreditation to attract patients.

--Lani Luciano