Twenty two Muslim diabetic patients on oral hypoglycaemic agents were studied during the fasting month of Ramadan to determine the effect of fasting on their diabetic control. All the patients completed their fast during the month. Their mean (+/- standard deviation) blood glucose, serum fructosamine and body weight before the fasting month were 10.7 +/- 4.6 mmol/l, 6.64 +/- 3.64 mmol/l and 60.5 +/- 12.6 kg and by the end of the fasting month were 10.9 +/- 4.4 mmol/1,4.34 +/- 1.08 mmol/l and 59.8 +/- 12.3 kg respectively. There was no significant difference between the blood glucose levels but there were significant reductions in the mean body weight and fructosamine values (p = 0.01 and p = 0.03 respectively). The mean decrease in body weight and fructosamine were 0.7 +/- 1.3 kg and 2.29 +/- 3.09 mmol/l respectively. There were also statistically significant differences between the mean daily calorie content before the fasting and during the fasting month (1480 +/- 326 vs 1193 +/- 378 Cal/day - p less than 0.005) and between the mean daily carbohydrate content (389 +/- 298 vs 187 +/- 46 gm/day - p less than 0.005). In conclusion, fasting was safe for diabetic patients on oral hypoglycaemic agents and it was associated with weight reduction and improvement in the overall diabetic control. This was most likely due to decrease in food intake.