This article describes an evaluation of the implementation of a cholesterol management program in family physicians' offices as part of the Physician-Based Nutrition Program to Lower Coronary Heart Disease Risk (PBNP). The evaluation, conducted through a partnership evaluation model, used multiple case study methodology and combined the use of quantitative and qualitative methods. Data sources included office staff reports and interviews, records of contacts with study personnel, patient care data, and patient telephone interviews. Data from these sources revealed gradual program implementation and considerable variation in practitioner and clinic involvement in cholesterol management. Clinic staff reported that the support provided by PBNP in the form of training, operations materials, patient education materials and ongoing assistance was very useful. This formative evaluation has implications for refinement of the PBNP and for other prevention programs in primary care settings. It demonstrates the feasibility and acceptability of a systems approach to physicians, cholesterol/nutrition educators and clinic support staff. It also suggests ways in which researchers and clinicians can implement and evaluate health care innovations.