AbstractThe prevalence of HTLV‐I antibodies was evaluated in Jamaica among persons with various malignant, infectious, autoimmune and hematologic disorders and in clinically normal persons. Results document that: (1) the prevalence of HTLV‐I antibodies in this population increases with age; (2) overall, there is no significant difference in the antibody prevalence between males and females; (3) antibody‐positive individuals are born in all major regions of the island and geographical variance in antibody prevalence by place of birth was not prominent; (4) there is further confirmation of the high prevalence of HTLV‐I antibody‐positive lymphomas in Jamaica; and (5) the prevalence of HTLV‐I antibodies in hemophiliacs, patients with chronic lymphocytic leukemia (CLL), myelogenous leukemias, and patients with breast cancer is higher than in the age‐matched population without malignancies, although none of these differences were statistically significant. The increased prevalence in hemophiliacs is most likely related to their frequent transfusion with blood products, but it has not yet been determined whether the prevalence in patients with other diseases is related to their diseases or other as yet undefined factors in common.