This study examines the costs of running a method of systematic care for diabetic patients in one general practice--the monthly 'diabetic day'. Doctor, nurse, chiropodist, dietitian, clerical officer, building and stationery costs were included in the evaluation. The study took place in an inner city practice of seven partners based in a health centre. The cost per year of running the diabetic days was 1854.53 pounds to the practice and 4465.69 pounds to the National Health Service (1989 prices). The cost to the practice included family health services authority reimbursements and excluded the cost of the chiropodist and dietitian. The cost per attendance was 38.17 pounds to the NHS and 15.85 pounds to the practice while the cost per patient per year was 58.00 pounds to the NHS and 24.08 pounds to the practice. The practice suffered a net loss after taking into account health promotion clinic payments received from the family health services authority. The cost to the NHS of each attendance at the practice was considerably greater than estimates of the cost of attendance at the outpatients department of a local trust hospital. However, it is argued that general practice has an essential role in the improvement of diabetic surveillance, and that an adequate remuneration package could transform the care of many patients with diabetes.