1 Fourteen maturity onset diabetics showed improvement of glucose tolerance while on treatment with clofibrate. Fasting blood glucose levels were reduced by 20% after treatment for 14 and 28 days. 2 The effect was found to be independent of concurrent treatment with oral hypoglycaemic drugs. 3 Plasma insulin levels were also lower during clofibrate treatment. 4 Clofibrate may prove to be a useful adjunct to the treatment of maturity onset diabetes.