The human immunodeficiency virus is the etiologic agent of the acquired immunodeficiency syndrome, which currently infects more than 30 million people. Heterosexual transmission of the virus has become the leading route of transmission of human immunodeficiency virus both in the United States and worldwide. Cutaneous diseases are common manifestations of human immunodeficiency virus infection, developing in more than 80% of patients at some time during their illness. HIV-infected persons have impairment of cell- mediated immunity and may have infectious or neoplastic syndromes develop that are specific for acquired immunodeficiency syndrome and rarely seen in persons not infected with human immunodeficiency virus. Many serious or life- threatening illnesses may be seen initially with cutaneous findings. Patients infected with the human immunodeficiency virus may also have unusual manifestations of common dermatologic diseases and frequent cutaneous eruptions from medications develop. Cells of monocyte/macrophage lineage often possess CD4 receptors and are targets of infection with the human immunodeficiency virus. Epidermal Langerhans cells are abnormal in both number and function in vitro and probably in vivo, also contributing to the frequency of skin involvement in patients infected with the human immunodeficiency virus. The incidence of skin disease increases with the progression of immunodeficiency.