We report on three young females complaining of bloody diarrhea of acute onset due to hemorrhagic colitis associated with oral amoxicillin therapy. The bloody diarrhea with abdominal cramps began 4 to 6 days after starting the treatment. Right colon was involved in two patients, and the descending and sigmoid colon in the other. Stool cultures and search for Cl. difficile toxins were repeatedly negative. Biopsy revealed marked mucosal hemorrhage (2/3), erosions (2/3) and thrombosed vessels (2/6). Symptoms rapidly resolved after 2 to 6 days. Extensive allergic evaluation in one patient did not reveal a hypersensitivity reaction. A literature review reveals another 31 patients with this characteristic form of colitis associated with ampicillin or amoxicillin therapy.