It is widely accepted that patient education is an essential adjunct to the care of diabetic patients. A randomised controlled clinical trial in patient education was conducted at a diabetic and general medical clinic in Sri Jayawardenepura General Hospital. Two groups of diabetic patients matched for age, gender and duration of diabetes were allocated randomly to conventional care at general medical clinics or to a diabetes clinic where specific educational objectives were defined and patients trained to achieve these objectives. The doctors treating these patients were not 'blinded' to treatment groups. Diabetes knowledge was assessed using a diabetes knowledge scale and metabolic control assessed by mean fasting blood glucose. The patients attending the diabetic clinic showed significant improvement in both knowledge scores (67% vs 34%, p < 0.01) and mean fasting blood glucose 6.38 +/- 0.85 mmol/l vs 9.7 +/- 1.7 mmol/l, p < 0.01) at 6 months. We conclude that diabetes education improves patient knowledge and diabetes control.