BACKGROUND: Dermatological manifestations affect 5% of patients with human T-lymphotropic virus (HTLV). METHODS: Thirteen patients with inflammatory or lymphoproliferative dermatological diseases, both HTLV-positive and HTLV-negative, were selected for treatment with ultraviolet B narrowband (UVB-NB) phototherapy. Clinical and histopathological evaluations were conducted before and after 120 d of phototherapy. RESULTS: All seven HTLV-positive patients evaluated were type 1. Clinical evaluation showed improvement in all 13 patients. In the histopathological examination, all patients with lymphoproliferative diseases and five with inflammatory diseases showed regression in most of the assessed parameters. CONCLUSIONS: The present research suggests that UVB-NB phototherapy is a promising treatment for lymphoproliferative and inflammatory skin diseases in HTLV-1 patients.