Neutropenic enterocolitis is a necrotizing enterocolitis of the cecum and right colon that is most frequently seen in leukemia patients undergoing chemotherapy. It has also been described in other neutropenic states. Clinical recognition of this condition is very difficult, and it is seldom diagnosed antemortem. If left untreated, the condition rapidly progresses to sepsis and eventually to death. Here we present a case of neutropenic enterocolitis in a severely ill patient with acute myelogenous leukemia (AML). A 49-year-old female with AML underwent re-induction chemotherapy. She became febrile four days after the completion of chemotherapy and complained of severe abdominal pain. The granulocyte count was 0 at this time. Real-time ultrasonographic examination of the abdomen revealed a marked thickening of the ascending colon wall, and especially of the cecum and terminal ileum. The lumen was anechoic, indicating that it was filled with fluid. A diagnosis of neutropenic entrocolitis was performed, and the partient was treated conservatively with parenteral antibiotics and granulocyte transfusion. However, she eventually died of sepsis. An autopsy showed significant submucosal edema of the involved colon. Early diagnosis is of paramount importance for the effective management of this condition. Ultrasonography provides a rapid and noninvasive diagnostic technique for this condition in severely ill patients.