In the present study the effect of short-term metabolic control on plasma lipids and apoproteins in a group of subjects with type II diabetes mellitus in insulin treatment for secondary failure to oral agent therapy (sulphonylureas) was examined. For this reason 40 diabetic patients and 40 normal controls were studied. The lipoapoproteic pattern at the admission in the study and after a steady metabolic control, achieved by conventional insulin therapy and estimated by seric fructosamine, was evaluated. Diabetic patients, when compared with normal controls, showed a more atherogenic lipo-apoproteic profile and after achieving metabolic control, showed a reduction of triglyceride and apo B levels and a significant increase of the apo AI levels. The achievement of a good metabolic control, even after a short time, was associated with an improvement of the lipo-apoproteic profile, altered in diabetes mellitus in secondary failure.