Blood lipid values, clinical data and effects of therapy are reported on 74 patients with hyperlipidemia and xanthomatosis. A natural subdivision into two groups was observed on the basis of low density lipoprotein lipid values: one corresponding to Frederickson's type II, characterized by elevated low density lipoproteins, tendinous xanthomata, absence of eruptive xanthomata and a high incidence of cardiovascular diseases and the other resembling Frederickson's type III, with elevated very low density lipoproteins, eruptive xanthomata, xanthomata striata palmaria, elevated cholesterol/triglyceride ratios in the very low density lipoproteins and irregular appearance of floating beta lipoproteins. The latter group consisted of 32 patients in whom cardiovascular symptoms were relatively rare, despite mean cholesterol levels of 500 mg/dl.