A 63-year-old man was referred to our department on September 14, 1992, because of multiple red papules with severe itching. Pruritic papular eruption (PPE) in a human immunodeficiency virus (HIV)-infected patient was diagnosed based on the histological findings, the reduction in CD4, and positive results for HIV antibody. In September of 1993, papules and erythematous plaques with scales appeared on both the palms and soles. The erythema was pruritic and spread gradually to the extremities and trunk. These plaques with erythema and scales are similar to those of the psoriatic lesions seen in Reiter's syndrome, although the HLA typing was not B27. Immunohistopathological findings of the papules of PPE and plaques of psoriasiform lesions showed that perivascularly infiltrated cells in the dermis were mostly lymphocytes. The lymphocytes in PPE were positive for CD45 and negative for CD3, CD43, and CD45RO, but the lymphocytes in psoriasiform lesions were positive for CD45, CD3, and CD43. Moreover, 20-30% of these lymphocytes were also intensely positive for CD45RO. These observations were similar to those obtained in the lesional skin of HIV-negative psoriasis, suggesting that there were no significant immunohistopathological differences in the abnormality of local cellular immunity related to the formation of psoriasiform lesions in HIV-negative psoriasis and HIV-positive psoriasis.