PURPOSE:A patient with a solitary colonic ulcer had sudden onset of crampy abdominal pain, anorexia, fever, and vomiting, with signs of positive peritoneal irritation.METHODS:The diagnosis was proved by histopathologic examination of right hemicolectomy material.RESULTS:An emergency laparotomy, with right hemicolectomy and ileotransversostomy, gave complete relief from symptoms. The patient was still asymptomatic at the two‐year follow‐up, and control colonoscopic examinations performed at 6 and 18 months after the operation were normal.CONCLUSION:Preoperative diagnosis of perforated solitary colonic ulcers localized at the right hemicolon may mimic acute appendicitis, and intraoperative findings may mimic colonic carcinoma. If the preoperative diagnosis is not certain, right hemicolectomy and ileotransversostomy, with regular colonoscopic controls, is a safe procedure in the treatment and follow‐up of these patients.