Serum lipid concentrations were assessed in 147 type 2 diabetics. The patients were divided into different sub-groups in order to follow up different factors which could have an impact on serum lipids. The mean total cholesterol concentrations were significantly higher in diabetic women as compared with men. The authors did not reveal significant differences in lipid concentrations between obese and non-obese diabetics. Hypertensive diabetics had higher mean total cholesterol levels and LDL-cholesterol levels, as compared with diabetic patients without hypertension. Patients using oral antidiabetics had significantly higher mean triglyceride levels and lower HDL-cholesterol levels, as compared with insulin-treated diabetics. In a multiple stepwise regression analysis correlated triglycerides with three independent variables: total cholesterol, diastolic blood pressure and inversely with HDL-cholesterol. On the other hand, total cholesterol correlated significantly with triglycerides, HDL-cholesterol and proteinuria/day. To sum up, it may be stated, that the results of the present investigation are consistent with Reaven's concept of the syndrome X, however the cholesterol concentration is affected also by the proteinuria.