ObjectiveTo sum up the diagnosis and treatment of adult ileal duplication with clinical cases from Peking Union Medical College Hospital (PUMCH). MethodsSix cases of adult ileal duplication admitted in our hospital from February 1996 to December 2010 were analyzed. Different assistant investigations were supposed to different patients due to the chief complaints including gastroscope, colonoscopy, abdominal CT scan, arteriography, 99Tcm radionuclide imaging, and double-balloon intestinal endoscope. None was made a definite diagnosis before operation with only one uncertain case. All cases received operation and pathological examination. Results All cases admitted were male. The chief complaints included intestinal bleeding, abdominalgia, intestinal obstruction, and abdominal mass. Five out of six patients received gastroscope, colonoscopy, and abdominal CT scan while three received mesenteric arteriography, but none was found any suggestion for ileal duplication. Even 99Tcm radionuclide imaging pointed out only two with abnormal abdominal bleeding. Three received doubleballoon intestinal endoscope, paying attention that only one discovered with ileal duplication. In a concluding, none was made a definite diagnosis before operation with only one uncertain case. All the cases received operation. The duplications of ileum in the length of 6-25 cm were found at the site of 11-100 cm proximal to ileocecum during the operation. Pathological report confirmed the clinical diagnosis of all cases with adult ileal duplications． Two cases were found with ectopic gastric mucosa, another two with diverticulum, and one with ectopic pancreas， in addition the remaining with inflammatory fibrous pseudotumor. Prognosis were good for all after operation. ConclusionsIleal duplications are rarely seen in adults, gender prefer male． Without specific clinical symptoms and inspections, definite diagnosis before operation is hard to make. But maybe doubleballoon intestinal endoscope and 99Tcm radionuclide imaging can give out positive result. Surgeons should be aware of this condition when performing abdominal exploration. Once discovered, resection is necessary.