Between 1982 and 1995, over 700 HIV-infected patients with different skin diseases were registered at the Department of Dermatology, Benjamin Franklin Medical Center, The Free University of Berlin. Thirty-six of them (approximately 5%) were diagnosed as having psoriasis. This is clearly a higher prevalence of psoriasis than in the general population (1-2%). If psoriasis lesions are not clinically seen before diagnosis of HIV infection, the disease will preferentially (approximately 80% of these cases) appear during the late stages of the infection (CD4/CD8 ratio < 0.4). Six of the 36 patients with HIV-related psoriasis (= 16%) were found to have severe disease, showing an exsudative clinical picture. In this paper we report in detail on two representative cases from this group of patients. Histological examination also revealed exsudative changes in HIV-infected patients with clinically moderate psoriasis. Immunohistochemically, HIV-related psoriasis showed a moderately decreased number of infiltrating T-cells, in contrast to psoriatic skin from non-infected patients. A marked difference was the reduced expression of the lymphocyte antigen OPD-4 in HIV-related psoriasis. Routine antipsoriatic treatment modalities in combination with systemic retinoids and phototherapy (SUP/PUVA) were successful in the treatment of severe exsudative psoriasis in HIV patients, but the course of the disease was prolonged and exacerbation was more frequent. HIV-related psoriasis was found not to influence the underlying HIV infection.