BACKGROUND: Large trials of primary care-based health promotion to modify coronary heart disease risks have shown only modest benefits. Could more intensive intervention, with doctors sharing with practice nurses in health promotion, produce better health outcomes in the context of the small family practice? How cost-effective might these interventions be? AIM: To assess the cost-effectiveness of an intensive programme of coronary heart disease (CHD) risk factor modification in a rural general practice in which doctors had a major input. METHOD: A longitudinal study of changes in risk factors in a group of adult patients identified as having one or more major CHD risk factor and monitored for one to seven years. Patients were recruited from and followed up in health promotion clinics, routine practice nurse appointments, or routine doctors' surgeries. All received the practice's routine interventions to modify risk, and changes in risk factors were recorded. Time spent by members of the primary health care team on CHD health promotion was recorded over a two-year period. RESULTS: From a practice list of 2040, 760 patients with one or more CHD risk factors were identified and followed up over a mean of 3.61 years (range six months to seven years). Significant improvements in each of the risk factors occurred, except in body mass index (BMI). Mean Dundee risk scores fell from 7.4 to 5.7 (by 23.3%). The annual cost to the practice (including doctor/nurse/secretarial time plus sundry practice expenses and laboratory costs, but excluding drug costs) was 6000 pounds. Cost per coronary death prevented was calculated as approximately 10,000 pounds. CONCLUSION: The results show an effect on risk factors broadly similar but slightly greater in magnitude than that achieved in the OXCHECK and British Family Heart Studies of nurse-delivered risk factor intervention in primary care. The results suggest that more intensive effort in lifestyle modification and health promotion, with more active involvement of doctors, could produce significant additional benefit. The cost-effectiveness of this approach compares favourably with many other accepted measures in coronary heart disease prevention.