Most cases of enterolith have been reported in association with the diverticula of small bowel. We report here a case of a patient in whom a huge enterolith developed in the afferent loop of Billroth II anastomosis with ensuing obturation obstruction. The enterolith was clearly shown on the preoperative abdominal computed tomograph and was removed through a duodenotomy. The postulated mechanism of the enterolith formation is impaired duodenal evacuatory motor activity due to previous gastrectomy.