Intestinal endometriosis mimics a wide variety of inflammatory, infectious, or neoplastic digestive diseases. To alert clinicians to its diverse manifestations, we describe nine patients who required laparotomy. The underlying diagnosis was elusive initially. In no case were symptoms clearly cyclic or temporally related to phases of the menstrual cycle. Presenting complaints included acute or subacute lower abdominal pain (three patients), hematochezia (two patients), signs or symptoms of small-bowel obstruction (two patients), peritonitis (one patient), and a partially obstructing sigmoid lesion (one patient). The findings of barium enema were nondiagnostic in the five cases in which it was performed. Surgery was needed in each case; indications included inability to exclude carcinoma (two patients), small-bowel obstruction (two patients), diffuse peritonitis (one patient), persistent colonic obstruction (one patient), pericolonic abscess (one patient), and intractable pain (one patient). Intestinal endometriosis has a diverse clinical spectrum, with nonspecific features in many patients. This disease should be considered during the evaluation of unexplained digestive complaints in women of childbearing years.