The clinical features of the first case of a patient with sitosterolemia and generalized eruptive xanthomatosis are described. A six-year-old girl with generalized eruption was referred to the lipid clinic because of the high plasma cholesterol levels determined by the enzymatic method. Neither clinical signs nor results of laboratory examinations appeared to be abnormal, except for the eruption and the increase in the plasma cholesterol concentration. A family survey revealed high plasma cholesterol concentrations in the mother and one of two other siblings. Histological examination showed the eruption to be a xanthoma. Plasma sterol analysis by high-performance liquid chromatography revealed a noticeable increase in plasma plant sterol as well as cholestanol concentrations in the proband and the hypercholesterolemic sibling. The other family members had slightly high plasma sterol concentrations. This is the first case of a sitosterolemic patient with eruptive xanthomatosis. The case indicates that the clinical features of the xanthoma in sitosterolemia are not only tuberous or tendon but also eruptive, and also suggests that sitosterolemia should be considered in the differential diagnosis of hypercholesterolemia in almost every case with tuberous or eruptive xanthoma. The diagnosis is clinically important, since the disease can be treated successfully by diet therapy and bile acid binding resins.