Recent investigations have confirmed the effectiveness and the excellent tolerability of pantethine, a derivative of pantetheine, an essential part of the acetylation coenzyme CoA, administered P.O., in normalizing the blood lipid concentrations of patients with hyperlipidemias. A group of 18 patients with hyperlipidemias (9 M, 9 F), with an average age of 52.6 years, was submitted to pantethine parenteral treatment. After a 20 days wash-out, pantethine (400 mg/day; BID) was administered intramuscularly, for 20 days. Total cholesterol, triglycerides, HDL-cholesterol, apo A-1 and B lipoprotein, uric acid in serum, glycemia, CBC, B.U.N., creatininemia, E.S.R., SGOT, SGPT, bilirubinemia, cardiac frequency, blood pressure and body weight were controlled before and after treatment. The drug showed to have a therapeutic effectiveness by a rapid and significant improvement in the blood lipid pattern with reduction of total cholesterol, triglycerides and apo-B lipoprotein and increase of HDL-cholesterol and apo A-1 lipoprotein. The tolerability of pantethine at the stated dosage and mode of administration was invariably excellent, with non complaints or visible side effects imputable to the test drug. BUN, creatininemia, glycemia, SGOT, SGPT, bilirubinemia, E.S.R., CBC, cardiac frequency and blood pressure readings showed no noteworthy changes throughout the study.