Objectives: To describe characteristics of low-back pain in human T-cell lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients and to identify its neuropathic and/or non-neuropathic pain components. Setting: A reference center for the care of patients with HAM/TSP in Rio de Janeiro, Brazil. Methods: A total of 90 patients with HAM/TSP referred by tertiary care centers were consecutively assessed. The patients were submitted to a clinical protocol that included Visual Analogue Scale (VAS), Timed Up and Go Test, Bodily Pain Domain of the Short Form 36 Health Status Questionnaire, Douleur Neuropathique 4 Questions (Neuropathic Pain 4 Questions) (DN4) and McGill Pain Questionnaire. Results: The prevalence of low-back pain in the studied sample was 75.5%; pain interferes with physical functioning and worsens with movement and physical effort. It can be relieved by analgesics and rest. Average pain intensity was 51.2 mm on VAS and 1.72 on DN4. The most frequent words used to describe low-back pain were throbbing, burning, jumping and aching. Surprisingly, 32.4% patients pointed the lower extremities as the most painful and used different descriptors. The most common drugs used were analgesics, nonsteroidal anti-inflammatory drugs and tricyclic antidepressants. Conclusions: Low-back pain in HAM/TSP patients has mainly nociceptive characteristics. Conversely, descriptors for lower extremities pain suggest a neuropathic origin.2020-12-19