To determine whether systemic lupus erythematosus (SLE) is associated with human T-lymphotropic virus, type I (HTLV-I) infection in Jamaica, an endemic area for the virus, we studied 63 patients with SLE at the University Hospital of the West Indies in Kingston. Antibodies to HTLV-I were measured by an enzyme-linked immunosorbent assay (ELISA) technique using purified disrupted whole virus as antigen, with confirmation by p24 protein RIA or competitive binding. Four of 63 SLE patients were HTLV-I seropositive (6.3%). There was no evidence for excess HTLV-I infection in SLE patients when their age- and sex-standardized HTLV-I seroprevalence rate was compared to that of a large group of healthy food service employees. None of 13 patients with rheumatoid arthritis were seropositive for HTLV-I. We conclude that HTLV-I infection does not appear to be linked with SLE in Jamaica.