Human T lymphotropic virus type 1 is associated with some neurologic diseases, mainly human T lymphotropic virus type 1-associated myelopathy/tropical spastic paraparesis. Human T lymphotropic virus type 2 has also been associated with similar cases of human T lymphotropic virus type 1-associated myelopathy/tropical spastic paraparesis, but evidences for a definitive relationship are less clear. On the other hand, neurologic manifestations of HIV infection are quite common, affecting more than one third of patients in HIV clinics. Seroepidemiologic studies show that HIV-infected individuals are at an increased risk for human T lymphotropic virus infection and vice versa in comparison with the general population. Furthermore, HIV/human T lymphotropic virus coinfection has been associated with distinctive immunophenotypes and an increased risk for development of neurodegenerative conditions. Thus, studies on HIV/human T lymphotropic virus coinfection have a practice clinical importance. In this review, we aim to discuss clinical and laboratorial data focusing on neurologic diseases in HIV/human T lymphotropic virus coinfection.