Endometriosis is sufficiently common that it should always be considered in the differential diagnosis of colon lesions of women of childbearing age. Seven selected cases illustrate problems in diagnosis and management of endometriosis of the colon. Characteristic of colon endometriosis are large bowel symptoms frequently associated with gynecologic complaints, usual sigmoid and rectosigmoid location, extramucosal radiologic appearance, and difficult diagnosis by endoscopic biopsy. Suspicion of malignancy and presence of a symptomatic colon lesion are indications for bowel resection, which is an effective form of therapy.