A 67-year-old man with celiac disease developed recurrent diarrhea, profound weakness and weight loss, with evidence of marked protein depletion. His clinical course was refractory to a strict gluten-free diet and steroid therapy. Postmortem studies led to definition of unrecognized collagenous sprue that caused ulceration and small intestinal perforation. Although PCR showed identical monoclonal T-cell populations in antemortem duodenal biopsies and postmortem jejunum, careful pathological evaluation demonstrated no frank lymphoma. Rarely, overt or even cryptic T-cell lymphoma may complicate collagenous sprue, however, small intestinal ulcers and perforation may also develop independently. The dramatic findings here may reflect an underlying or early molecular event in the eventual clinical appearance of overt T-cell lymphoma.