Unusual cutaneous vascular neoplasms distinct from Kaposi's sarcoma were observed in five patients with the acquired immunodeficiency syndrome (AIDS) or human immunodeficiency virus (HIV)-1 infection. The cutaneous lesions were solitary or multiple papules and nodules. In some patients the lesions also affected internal organs. Histologically the neoplasms were composed of proliferating blood vessels and cells with epithelioid features. Immunoperoxidase studies of one lesion showed that the cells expressed both factor VIII antigen, a maker for endothelial cells, and alpha 1-anti-chymotrypsin, a marker for histiocytes. In some patients the lesions gradually disappeared but in two they were the cause of death, in one case from disseminated intravascular coagulation and in the other from laryngeal obstruction by the tumour.