Hyporetinemia is associated with increased childhood morbidity and mortality that is reversible with vitamin A supplementation. Although vitamin A deficiency is otherwise rare in developed countries, the prevalence of hyporetinemia in human immunodeficiency virus (HIV)-infected persons is up to 29%. Hyporetinemic HIV-infected patients have a 3.5–5-fold increased risk of death. Furthermore, HIV-infected patients with very low or very high intake of vitamin A and β-carotene (a vitamin A precursor) have greater rates of disease progression than do patients with intermediate intake. In developing countries up to 60% of HIV-infected pregnant women are hyporetinemic. In such women the relative risk of perinatal HIV transmission may be increased more than fourfold. These data indicate that vitamin A deficiency is common in HIV-infected patients in the developed world and strongly suggest that vitamin A supplementation may be especially useful in adjunctive therapy for HIV-infected pregnant women who reside in the developing world.