We followed 24 patients with HTLV-I-associated myelopathy (HAM) for 4-12 years (mean 7 years) and assessed longitudinal changes of their spastic paraparesis by Kurtzke's Disability Status Scale (DSS). The DSS score of spastic paraparesis was unchanged in 18 patients (75%), advanced (worsened) by two in 1 patient and by one in 3 patients, and declined (improved) by one in 2 patients during the follow-up period. The results demonstrated that HAM presents with a variety of clinical courses including spontaneous improvement.