Human T-cell lymphotropic virus type I is an oncogenic retrovirus, endemic in Southwestern Japan, the Caribbean, some parts of Africa and Central and South America. The virus is etiologically associated with adult T-cell leukemia/lymphoma and a myelopathy called tropical spastic paraparesis or HTLV-I associated myelopathy. Transmission of the virus is almost identical to that of HIV. The latency period before onset of clinical symptoms can last from a few years (tropical spastic paraparesis) up to several decades (adult T-cell leukemia/lymphoma). Four different clinicopathological subtypes of the T-cell neoplasia are known, and in this article we describe two patients with the subtype lymphoma.