Infection by human T-cell lymphotropic virus type I (HTLV-I) is associated with neurological diseases, malignancies, and other less common pathologies. In addition, infection by HTLV-I has been implicated in some degree of immunological impairment. Some previous reports detected an association between HTLV-I infection and an increased rate of antibodies against S. stercoralis, as well as a higher frequency of S. stercoralis carrier state. Here, we report a case of a chronic, recurrent S. stercoralis parasitism in a patient infected by HTLV-I. The patient demonstrated evidence of immunosuppression characterized by skin allergy to common antigens, oral candidiasis and severe, recurrent diarrhea caused by S. stercoralis. The infection requires maintenance of suppressive therapy to control diarrhea and its consequences. We postulate that S. stercoralis may act as an opportunistic agent in patients infected by HTLV-I.