A serological survey for the presence of antibodies against the human T-cell leukemia virus, type 1 (HTLV-1) in patients seen at the Chubu Hospital in Okinawa was undertaken. All patients with the clinicopathological diagnosis of adult T-cell leukemia-lymphoma were positive. These cases had the characteristic features of adult T-cell leukemia-lymphoma: diffuse histology, often mixed cell or pleomorphic, and a high frequency of hypercalcemia, leukemic phase, diffuse visceral involvement, and opportunistic infections. The median survival of these patients was short, being only 18 weeks. Of the other patients with cancers screened, two of five other non-Hodgkin's lymphoma patients were positive and three of eight patients with other hematological cancers were positive. In addition, three of the four immediate family members of one adult T-cell leukemia-lymphoma case had antibodies. Of the other persons (both in- and outpatients) without hematological cancers, those under the age of 50 had a much lower antibody prevalence (4%) than those over 50 (30%). There was no significant difference in antibody prevalence between the two sexes in either the younger or older age group. These findings further document that Okinawa is an endemic area for HTLV-1. None of the 157 individuals screened for antibodies to HTLV-3 were positive, consistent with the fact that no cases of the acquired immune deficiency syndrome have been reported from Okinawa.