Using a panel of monoclonal antibodies, we have studied cell surface antigens of infiltrating mononuclear cells in skin biopsies from patients with cutaneous T-cell lymphoma (CTCL) and compared them with the T-cell surface phenotype seen in benign cutaneous T-cell infiltrations (e.g., contact dermatitis, delayed hypersensitivity skin tests, granuloma annulare) and in dermal infiltrates of lymphomatoid granulomatosis patients. We found that unlike circulating CTCL (Sezary) cells, CTCL cells infiltrating skin epidermis frequently expressed the T-cell antigen 3A1. Cutaneous infiltrates in 10 patients with mycosis fungoides (MF) and 1 patient with Sezary syndrome were OKT4 (inducer T cell), OKT8 (suppressor/cytotoxic T cell); 2 patients with MF were OKT4- , OKT8; and one MF patients's skin T cell were OKT4-, OKT8+. Similar to CTCL infiltrating cells, most of the benign skin T-cell infiltrates were usually 3A1+. OKT4+, and OKT8-. Our study shows the complex nature of T-cell antigen patterns in inflammatory and malignant skin T-cell infiltrations. We demonstrated that the CTCL the skin epidermal infiltrating T-cell phenotype is not invariate, and in many cases, is similar to the phenotype of clinically benign cutaneous T-cell infiltrations.