A 66-year-old male heterozygous familial hypercholesterolemia (FH) patient with significant coronary atherosclerosis has been treated by us with probucol (1000 mg daily) for eight years. This treatment has produced significant reductions in the cholesterol levels of his serum, low density lipoprotein (LDL), and high density lipoprotein (HDL) from 237 +/- 20 mg/dl (mean +/- S.D.) to 156 +/- 15, from 175 +/- 8 to 111 +/- 16 mg/dl, and from 23 +/- 4 to 19 +/- 2 mg/dl, respectively. These reductions have been maintained for eight years. Serum triglyceride levels also decreased, from 220 +/- 54 to 146 +/- 36 md/dl. During this period, marked regression of xanthomas on the eyelids and finger extensor tendons was observed, while thickness of the Achilles tendons was reduced from 21.0 mm to 13.0 mm. On other hand, effort-induced anginal symptoms requiring additional antianginal medication have been noticed, and angiographically-demonstrated coronary atherosclerosis has progressed significantly during these eight years. These observations lead us to suggest that maintaining low levels of HDL cholesterol with probucol, even though resulting in satisfactory reduction of LDL cholesterol and marked regression of xanthomas, appears to be associated with the progression of atherosclerosis in the coronary arteries.