A 36-year-old Hispanic man who had undergone allogeneic bone marrow transplantation, complicated by graft versus host disease, was admitted with acute gastrointestinal symptoms, including severe diarrhea and diffuse abdominal pain. He also had a persistent cough with sputum production. Blood cultures yielded Escherichia coli, and sputum cultures grew Apergillus species. The patient was treated with antifungal agents and broad-spectrum antibiotics. Despite aggressive medical therapy, the patient died 10 days after admission. Postmortem examination disclosed severe, bilateral confluent bronchopneumonia, with numerous septated branching hyphae consistent with Aspergillus species fungal organisms that involved the pulmonary parenchyma and tracheobronchial tree. Although the small and large bowels were only mildly congested, the entire gastric mucosa was covered with a 1.5-cm-thick pseudomembrane that contained numerous Aspergillus organisms. Our report represents the first description, to our knowledge, of a diffuse inflammatory pseudomembrane in the stomach, a complication that to date has only been associated with small and large bowel involvement.