Colombia is one of the endemic zones for human T Lymphotrophic adult cell Leucemia/ Lymphoma type I and II (HTLV I-II). However, screening for this microorganism has not been adequately structured in our country, exposing the population to a great risk of transfusional dissemination. A revision is made of the main epidemiological and clinical features of the infection in humans, which is characterized by a chronic, latent and asymptomatic infection. When there is a manifest clinical picture it includes adult T cell Leukemia of the adult and a form of myelopathy known as tropical spastic paraparesia. There are a number of associated clinical entities for which a causal relationship has not been fully elucidated.