A probability sample of all patients seen in the four health maintenance organization (HMO) primary care clinics in one Northern California county (N = 314) are compared to patients from all five of the county-operated primary care clinics in the same county (N = 394) and to the general population of the county (N = 3069) on demographic characteristics, drinking patterns and alcohol-related problems. The HMO clinic patients were less likely to report frequent, heavy drinking, drunkenness or alcohol-related problems during the last year compared to those in the county clinics sample, and they were also less likely to report heavy and problem drinking compared to those in the general population. These data suggest problem drinking may not be over-represented in primary care practice in general, but rather may be more closely associated with characteristics of clientele served by a primary care practice than with those characteristics associated with a need for medical attention.