The main neurological manifestation due to Human T-Cell Lymphotropic Virus type (HTLV1) infection is a chronic spastic paraparesis called HTLV1-associated paraparesis (HAP). Since 1985, we observed in Martinique (French West Indies) 276 cases of HAP. Among them, 70 patients fulfilled clinical, electrophysiological or histological criteria of associated peripheral nervous system involvement (42/70), myositis (8/70), or both (20/70). Muscle biopsy revealed neurogenic atrophy of muscle fibers or myositic changes in 41/70. Neuromuscular involvement was only mild in 19/70. On the other hand, 25 patients presented with a syndrome mimicking amyotrophic lateral sclerosis, and 7 other patients with features of polymyositis. This study shows that neurological manifestations associated to HTLV1 infection may be more complex than the well-known chronic spastic paraparesis, since 25.4% of the HAP Martinican patients exhibit neuropathic or myositic features.