Pancreatic endometrial cyst is an extremely rare instance of ectopic endometriosis that was first described by Marchevsky in 1984. A 21-yr-old woman with a history of epigastric pain and weight loss was found to have a cystic lesion in the pancreas on CT-scan. Under the tentative diagnosis of a pancreatic cystic neoplasm, partial pancreatectomy was performed. Histopathological examination of the specimen revealed cystic endometriosis. The clinicopathological features of the lesion are discussed and literature concerning this extremely rare lesion is reviewed.