The prevalence rates of xanthelasma and corneal arcus were computed for normolipidemic and dyslipoproteinemic participants in the Lipid Research Clinics population surveys. The prevalence of both xanthelasma and corneal arcus increased with age, was highest in persons with type II phenotype, and usually low in those with type IV phenotype. The relative effects of age and use of gonadal hormones were different in the two lesions. Both xanthelasma and corneal arcus were associated with increased levels of plasma cholesterol and low-density lipoprotein cholesterol (LDL-C), especially in young males. In general, persons with either lesion had increased odds of having type IIa dyslipoproteinemia but decreased odds of having type IV. Xanthelasma and corneal arcus were highly associated with each other, especially in young people. There was no consistent univariate association of xanthelasma and corneal arcus with smoking, alcohol consumption, blood pressure, obesity, sedentary lifestyle, family history of ischemic heart disease, or glucose and uric acid plasma concentrations. Adjusted odds ratios for ischemic heart disease in participants with xanthelasma and corneal arcus were generally increased, except in older female nonusers of gonadal hormones, in whom they were significantly decreased. Neither xanthelasma nor corneal arcus showed a consistent association with manifestations of peripheral arterial disease. Thus the clinical findings of xanthelasma or corneal arcus, especially in young people, seem to identify persons with plasma lipoprotein abnormalities.