We describe a 40-yr-old woman who presented with abdominal pain and diarrhea, and who was found to have segmental colitis involving the cecum and ascending colon. Aeromonas hydrophila was isolated from the stool, and her symptoms responded to appropriate antibiotic therapy. Follow-up colonoscopy confirmed complete endoscopic and histologic resolution of her colitis. This report further supports the belief that Aeromonas species are pathogens in healthy humans. This organism needs to be considered in the differential diagnosis of diffuse and segmental colitis.