This study was designed to assess the effects of fasting during Ramadan on weight, blood pressure, metabolic control and plasma lipoproteins in diabetic patients. This study was conducted in December 2000 (Ramadan 1421) when the length of fasting was 12 hours a day. It included 38 type 2 diabetic patients (20 males and 18 females). Mean patient age was 51.410.5 years and mean body mass index (BMI) 28.94.7kg/m2. Three patients were treated with diet and 35 with oral hypoglycemic agents. Clinical and biochemical parameters were evaluated during three periods: three weeks before Ramadan (T0), at the fourth week of Ramadan (T1) and three weeks after the end of Ramadan (T2). During the month of Ramadan, a decrease in weight (0.52kg) and no change in blood pressure were observed. No metabolic complication occurred in our patients. A significant effect of Ramadan fasting was observed on glycemic control and lipoprotein levels. In patients whose fructosamine level before Ramadan was higher than 340micromol/l, plasma fasting glucose and serum fructosamine increased during Ramadan (p<0.003) and returned to initial levels at the end of Ramadan T2; in these patients also, a decrease of HDL-cholesterol (p<0.01) associated with an increase of LDL-cholesterol (p<0.003) were observed at T1 and disappeared at T2. But, in patients whose fructosamine level at T0 was lower than 340micromol/l, no effect on glycemic control and no significant effect on serum lipoprotein levels were found during Ramadan month. Ramadan fasting in type 2 diabetic patients seems to cause slight effects on glycemia and lipoprotein levels when previous metabolic control is quite good; but fasting induces more deterioration when previous control is poor.