The effect of fasting during the holy month of Ramadan on the metabolic control of 39 patients with overweight and non-insulin-dependent diabetes (NIDD) was studied. There were 29 females and 10 males with a mean age of 51.5 +/- 1.65 years and body mass index of 31.5 +/- 0.98 kg/m2. All were treated with diet and oral hypoglycaemic agents (OHA). There was no change in body weight, fasting plasma glucose, glycosylated haemoglobin (HbA1), C-peptide and insulin blood levels at the end of fasting. Total blood cholesterol concentration rose significantly (p 0.05) but not triglycerides at the end of Ramadan. There were no acute metabolic complications (e.g. hypoglycaemia) in the present study. We conclude that fasting during Ramadan is generally safe in NIDD. However, patients should be advised to make use of this opportunity to combine the spiritual benefit with improvement in the metabolic control of the diabetes mainly through weight reduction.