Research has begun to identify elements in the practice environment that influence practice styles and health outcomes. One key element known to influence physician-patient interaction is the type of treatment environment: fee-for-service or health maintenance organization. Observers using the Davis Observation Code coded 82 physician-patient encounters in private practice settings and 72 encounters in a health maintenance organization. Populations were similar on all demographic measures except age, with health maintenance organization patients being older. Fee-for-service visits were shorter but included more coded behaviors per observation interval, resulting in equivalent total numbers of coded behaviors in each type of visit. Health maintenance organization visits included significantly more patient questions, preventive services, disease prevention, treatment planning, and discussion of substance use. Results may have reflected physician gender differences across sites or patient self-selection to sites rather than site differences. These results have implications for developing further research to explore treatment environment, process, and outcome.