In 25 newly registered type II diabetics the effect of a sulfonylurea therapy with manilil in contrast to an exclusive dietary treatment on serum triglycerides, total cholesterol, HDL-cholesterol, LDL-cholesterol as well as the risk indices total cholesterol/HDL cholesterol and LDL cholesterol/HDL cholesterol were investigated within a period of treatment of 6 months. In comparable age, index of body weight and degree of the quality of metabolism (fasting blood glucose, HbA1) there are no differences between dietary treatment and combined diet-manilil-therapy concerning the lipid parameters investigated. There is a significant correlation between the quality of metabolism (fasting blood glucose concentration, HbA1), triglyceride and cholesterol concentration as well as the risk indices total cholesterol/HDL cholesterol and LDL cholesterol/HDL cholesterol. On the other hand, there is no relation between HDL cholesterol and the quality of metabolism. The findings do not speak for the fact that a sulfonylurea therapy is associated with an unfavourable effect on serum lipids, particularly on the HDL cholesterol.