In 60 patients with corneal arcus the incidence of hyperlipoproteinemia was examined by serum lipid and lipoprotein analysis. An elevation of the serum lipid, or lipoprotein contents was found in every patient. 52 patients showed a primary type II hyperlipoproteinemia, three had a type IV, and one a type V pattern. In three cases hyperlipoproteinemia was found to be secondary to a severe cholestasis. The results show that the occurrence of corneal arcus in nearly every subject under 50 years of age and in most subjects over 50 years of age is highly suggestive of the presence of type II hyperlipoproteinemia. Until atherosclerotic complications appear, the course of the type II hyperlipoproteinemia is lingering and shows poor symptoms. Therefore, corneal arcus is of special importance for the early detection of this type of hyperlipoproteinemia.