A man in his 50s was referred to the hospital with fever, right lower abdominal pain, and bloody diarrhea. Based on computed tomography images and characteristic varioliform erosions observed during the colonoscopic examination, the patient was diagnosed with fulminant amebic colitis. Intravenous metronidazole was administered immediately. After symptom improvement, a second colonoscopic examination revealed inflammation localized to the right hemicolon. A right colectomy was performed on the 75th hospital day, and the patient was discharged without further problems. Prompt antiamebic therapy based on early endoscopic diagnosis was effective in quelling colonic inflammation in a life-threatening case of acute fulminant amebic colitis. Moreover, colonoscopic reexamination was useful in determining the extent of inflammation and minimizing colon resection.