A survey of patients' waiting times was performed in the follow-up clinics of a large hospital outpatient diabetic department (approximately 6500 patients). Over a period of 1 week, 138 patients attended 5 review outpatient clinics. The overall patient:doctor ratio was 11.1:1. Only 18.8% of patients were seen by the doctor, and 86% by the nurse within 30 min of their appointment time. A policy of strict adherence to the formal appointment times was implemented but had no effect on the waiting time (20% of patients were seen by the doctor, and 82.2% by the nurse within 30 min of their appointment time). The combined effects of adherence to actual appointment times and increasing the number of doctors (lowering the patient:doctor ratio to 7.7:1), reduced the total waiting times, and increased the proportion of patients seen by the doctor or nurse within 30 min of their appointment time, to 31% and 100%, respectively. Strict adherence to appointment times was difficult to implement and ineffective but the patient:doctor ratio was important in determining waiting times in the diabetic clinic. Inadequate medical staffing of diabetic outpatient clinics is a major cause of prolonged waiting time for patients. This approach may be useful in assessing and improving the organizational efficiency of a diabetes service.