METHODS A 25-year-old woman had for 5 years complained of lower and mid-abdominal pain, at first monthly but later continuous and gradually increasing in severity. At the same time she had diarrhoea associated with nausea, vomiting and weight loss. Physical examination showed a markedly distended abdomen, diffuse pain on pressure over the whole abdomen, most marked in the left middle and lower part, and high pitched peristalsis, but was otherwise unremarkable. METHODS Abdominal radiography indicated small-intestinal ileus, while ultrasound revealed absent peristalsis in the small intestine and a 10 cm stenosis in the terminal ileum. Coloscopy demonstrated a fibrosed stenosis of the terminal ileum but a biopsy showed no specific changes. METHODS Under suspicion of Crohn's disease with stenosis of the terminal ileum a partial resection of the ileum was performed. The ileum was on inspection thickened with scar tissue but no inflammation. Histology revealed florid chronic mucosal and submucosal inflammation, haemorrhages and ulcers, as well as numerous islands of endometriosis in the subserosa and muscularis propria. CONCLUSIONS Endometriosis is a rare disease in women of the reproductive age, but should be considered in the differential diagnosis of Crohn's disease of the terminal ileum.