Xanthomas and lipoprotein abnormalities are important to all physicians. Many factors affect the synthesis and degradation of cholesterol and triglyceride, the lipids of major importance in these disorders. Lipids travel in serum bound to protein moieties, forming lipoproteins. Hyperlipoproteinemias may be either primary or secondary to other diseases. Primary hyperlipoproteinemias recently have been reclassified, based on genetic studies. The four types of xanthomas include tendinous, tuberous, eruptive, and planar. Since xanthomas are usually not diagnostic of a specific disease entity, history, physical, and laboratory data are required for appropriate classification and treatment.