Human T-lymphotropic virus type I (HTLV-I)-associated tropical spastic paraparesis in Martinique has been identified in 54 patients, 49 women and 5 men. This myelopathy represents an endemic problem on this island and the earliest documented case dates from 1952. A blood transfusion history was obtained in 7 of the 54 patients (13%). There was a preponderance of cases from the northern Atlantic coast of Martinique, the most humid region on the island. The prevalence in this region reached 49.5 per 100,000, compared with the global prevalence of 11.9 cases per 100,000 for the island. An immune-mediated mechanism may be important in the pathogenesis of HTLV-I-associated tropical spastic paraparesis.