BACKGROUND Case studies from Project IMPROVE, the first randomized controlled trial to evaluate the effectiveness of continuous quality improvement (CQI) in primary care, were subjected to a qualitative analysis. Three questions were addressed: How does change in the health care environment affect a quality improvement (QI) process? How does clinic organization influence a QI process? and What is the impact of a QI process on clinic organization? METHODS Case studies were conducted in 6 clinics that had been randomly selected from the 22 clinics participating in the IMPROVE intervention. The case study data consisted of observations of CQI team meetings, open-ended interviews with 30 informants (team members plus others in the clinics), interviews with IMPROVE consultants, and documentation from the project. The data were analyzed to identify themes and generate concepts, assess and compare the informants' experiences, and develop a conceptual framework stimulated by research and theory literature. RESULTS Change and uncertainty in the health care environment both complicated the QI process and motivated participation in improvement. The smaller clinics appeared to have more difficulty with the QI process because of limited resources and lack of compatibility between the QI approach and their clinic organization. Project IMPROVE had two qualitative effects on clinics: increased awareness of preventive services and application of the CQI method to other problems and issues. CONCLUSIONS QI initiatives can help clinics adapt to a changing health care environment and create functioning teams or groups that can address a variety of organization problems and tasks. The process should be flexible to accommodate varying organization structures and cultures.