Acute abdominal pain, radiating to the right and left lower abdomen with pain on abdominal pressure developed in a 67-year-old man. There were questionable signs of peritonitis.Leukocytosis (20,000/microliter) and a high level of C-reactive protein (177 mg/l) were found. Ultrasound and computed tomography were suggestive of a stone in a Meckel's diverticulum.This diagnosis was confirmed at surgery and there were no other abnormalities. The diverticulum with stone was resected and the patient made an uneventful recovery.A stone in a Meckel's diverticulum, although rare, should be included in the differential diagnosis of acute abdomen with radiological evidence of calcification in the lower abdomen. The possibility of this rare complication raises the question of prophylactic resection of Meckel's diverticulum, even when it is merely an incidental finding.