A retrospective study was conducted in Martinique to identify patients with polyarthritis and positive serologic tests for the human T-cell lymphotropic virus Type I (HTLV-1). Patients with metabolic or bacterial causes of polyarthritis were excluded. We found 17 cases of HTLV-1-positive polyarthritis (6.7% of the total of polyarthritis patients followed in our department); there were 14 females and three males, and all the patients were West-Indian blacks. Mean age at diagnosis was 50 years. Five patients also had tropical spastic paraparesis. The polyarthritis was the inaugural manifestation of T-cell leukemia in one patient. Four patients had received blood transfusions. Fever, myalgia, and/or skin lesions were present at onset of the polyarthritis in seven cases. All 17 patients had peripheral, bilateral, symmetric polyarthritis; the most commonly involved sites were the hands (17/17) and knees (14/17). Three patients had rheumatoid factor and five had antinuclear antibody. Ten patients met at least four American Rheumatism Association criteria for rheumatoid arthritis; they accounted for 6.7% (10/150) of all polyarthritis patients managed in the same hospital department during the same period. We compared these ten patients with 20 HTLV-1-negative rheumatoid arthritis patients matched on gender, ethnic origin, and disease duration. There were no significant differences between the two groups for any of the parameters studied.