Studies of the prevalence of the human T-cell lymphotropic virus (HTLV-1) in 1984 to 1986 in the Republic of Panama revealed a national seroprevalence of 1 to 2%. Since 1985 clinical epidemiological studies of neurological diseases associated to HTLV-1 are being done. Two hundred and fitly six clinical cases of thirty eight different neurological diseases of unknown etiology studied in the Neurology Services of the Santo Tomas Hospital and the Social Security Metropolitan Hospital Complex have been associated in some way to the HTLV-1. Twelve cases of progressive spastic paraparesis were identified and related to HLTV-1 as an etiologic agent. The ratio of men to women was maintained at 1:1 with the average age at onset at 44 years and without racial preference. There are important doubts about the association of this virus to multiple sclerosis. The seroprevalence of the HTLV-1 virus in Panama is found to be similar to that reported in neighboring countries and the association of tropical spastic paraparesis to THLV-1 infection is identified.