Patients affected with Crohn's disease (CD) have a recognized, but low relative risk of developing small-bowel adenocarcinoma (SBA). In fact, SBA develops in 2.2% of patients who have long-standing CD and it is seldom diagnosed preoperatively because of its rarity. A retrospective analysis of all cases of SBA in CD patients since 1980 was carried out in Rouen University Hospital. Three patients with known or unknown CD who presented with SBA with long-term follow-up were analysed. In our first case, the occlusive syndrome revealed SBA and CD simultaneously. Most ileal carcinomas in CD are located in strictures and are often incidentally diagnosed postoperatively, as in our three cases. Digestive surgeons and gastroenterologists must be aware that the diagnosis of SBA in CD is often made fortuitously on histological examination after surgical resection for an occlusive syndrome. Failure to detect SBA in patients with CD results in late diagnosis, with poor survival.