It has been well established that psoriasis, psoriatic arthritis, and Reiter's syndrome can occur in patients with HIV infection. These arthocutaneous diseases tend to occur in temporal proximity to the development of AIDS and ARC, and their clinical manifestations are unusually severe. The appearance or exacerbation of psoriasis, arthritis, or Reiter's syndrome in a high-risk person should alert the clinician to possible underlying HIV infection. Treatment should be dictated by the severity of the skin and musculoskeletal disease as well as by the status of the immune system. Zidovudine appears to be effective in many diseases, especially psoriasis, and nonsteroidal antiinflammatory drugs are the mainstay for arthritis. Immunosuppressive agents such as methotrexate and azathioprine are contraindicated because they exacerbate immunodeficiency and promote infections. Epidemiologic studies suggest that the prevalence of these diseases, especially Reiter's syndrome, may be higher in HIV-positive populations than previously thought, especially in those patients with AIDS and ARC. Immunogenetic factors like HLA-B27 are important in the predisposition to Reiter's syndrome associated with HIV infection; however, it is not clear what role they play in HIV-associated psoriasis. Mechanisms underlying these observations remain unclear, although potential insights into the pathogeneses of psoriasis and Reiter's syndrome may be gained through future studies. Already it seems likely that CD4-positive helper T-cells, the target of HIV, are not necessary for the expression of psoriasis or Reiter's syndrome, and because of HLA class I associations, a role for CD8 positive cytotoxic T lymphocytes can be suspected. Infections, promoted by the profound immunodeficiency of AIDS, seem to be the most plausible explanations for the cutaneous and articular complications of HIV infection.