This report concerns three patients with human immunodeficiency virus (HIV) infection in whom malignant melanoma developed. One patient had metastatic malignant melanoma, one had iris melanoma, and one had a single skin melanoma. All three had lower absolute numbers of CD4+ cells than a control group, and the severity of their disease was inversely proportional to the absolute number of CD4+ cells. This report suggests an association between the immunodeficiency resulting from HIV infection and the development of malignant melanoma.