We have experienced a case with perforation after endoscopic balloon dilatation. The patient was diagnosed as having malignant lymphoma in the terminal ileum, and treated with eradication of H. Pylori and chemotherapy. The severe stenosis appeared at the same site of the tumor after the medical treatment. The first dilatation with a 15 mm balloon was successful. The lower small bowel obstruction occurred 14 months after the first balloon dilatation. The second dilatation with an 18 mm balloon was performed. The stricture site was remarkably dilated and could be passed by the scope. Perforation was confirmed because of the complaint of severe abdominal pain. The laparotomy finding showed the hole at the stricture site and remarkable fibrosis without tumorous tissue. The fragility of the tissue, the excessive inflation of the balloon and the insertion of the scope might be causes of the perforation. The case with severe stricture having almost no flexibility should be considered carefully in the determination of treatment procedures for the balloon dilatation.