Isolated gastrointestinal (GI) infiltrate is unusual at presentation or relapse of acute myelogenous leukemia (AML). We report a case of acute myelogenous leukemia (FAB-M4) whose isolated relapse presented as a bleeding gastric ulcer. The patient was a 30-year-old male who had been diagnosed to have AML in June 1988. While in third complete remission, he underwent a sibling allogeneic HLA-matched bone marrow transplant. Five months after transplantation, he was readmitted for pneumonia. While in the hospital, he had an episode of upper GI bleeding. The endoscopy revealed a leukemic gastric ulcer, with morphology and immunophenotyping identical to his initial AML. There was no evidence of leukemia in the blood or bone marrow. Although different types of leukemic infiltrates have been recognized at post-mortem examination, our case is unique because AML presenting as an isolated malignant ulcer has not been described previously. We conclude that relapsing AML may present as an isolated gastric ulcer and suggest that any suspicious lesion on upper GI endoscopy should be biopsied after aggressive platelet support.