We document an unusual case of HTLV-I positive adult T-cell leukaemia lymphoma (ATLL) in a 25 year old Chilean patient who presented with primary small intestinal involvement and during evolution developed a leukaemic phase. Duodenal biopsy showed infiltration by pleomorphic lymphoid cells with a CD45RO+ CD20- phenotype. Circulating lymphocytes had a convoluted nucleus and displayed a mature T-cell phenotype: CD2+, CD3+, CD4+, CD8-, CD25+, HLA-Dr+. HTLV-I serology was positive and HTLV-I retroviral sequences were demonstrated by PCR in the tissue. The patient was treated with chlorambucil and is well, disease free five years from diagnosis. Intestinal lymphoma as initial manifestation of ATLL is extremely uncommon, but when a T-cell lymphoma is detected in this localisation, in patients from a HTLV-I endemic area, retroviral studies are recommended in order to exclude an association with this retrovirus.