A daily 1000 mg of pantethine was orally administered to 12 male survivors of cerebral infarction for 3 months. Before and after the medication, plasma lipoproteins were ultracentrifugally separated. Plasma concentrations of total cholesterol, triglyceride, phospholipid, and VLDL- and LDL-cholesterol tended to decrease. On the contrary, HDL-cholesterol concentration and HDL:LDL-cholesterol ratio significantly increased. HDL2-cholesterol concentration significantly increased, whereas HDL3-cholesterol concentration remained unchanged, resulting in a significant elevation of HDL2:HDL3-cholesterol ratio. In HDL2 the percentage content of cholesterol and triglyceride decreased, while that of phospholipid increased. However, no significant changes were found in the chemical composition of HDL3. The plasma concentrations of apo A-I and, to a lesser extent, A-II increased, with a slight increase in A-I:A-II ratio but A-I:A-II ratio in either HDL2 or HDL3 remained unchanged.