A 75-year-old woman became ill suddenly with pneumonia two weeks after operation for colon cancer. Despite intensive support measures in the intensive care unit she died six hours after admission and 12 hours after her first symptom. Autopsy showed necrotizing pneumonia. Aeromonas hydrophila was isolated from a blood culture taken at admission and from the lung at autopsy. In patients who develop a fulminant disease of pneumonia, particularly those who have underlying medical conditions, Aeromonas hydrophila infection, though rare, should be considered.