The value of magnetic resonance (MR) imaging at 0.35 T in detecting, characterizing, and staging pelvic endometriosis was prospectively investigated in 30 consecutive women in whom this disease was clinically suspected. MR findings were correlated with the results of laparoscopy (13 women) and laparotomy (17 women). Surgical examination revealed a normal pelvis in five patients and endometriosis in 25. Three of the five normal cases and 16 of the 25 cases of endometriosis were correctly identified with MR imaging (sensitivity, 64%; specificity, 60%; accuracy, 63%). MR imaging demonstrated seven of eight endometriomas but only 14 of 29 adhesions and only six of 45 endometrial implants. While MR imaging demonstrated endometriomas, ovarian adhesions, and extraperitoneal endometrial implants, it could not accurately depict extraovarian endometrial adhesions and intraperitoneal endometrial implants. In addition, MR imaging findings did not correlate with the surgically determined severity of the disease. These limitations indicate that MR imaging cannot be used as the primary modality in the detection, characterization, and staging of endometriosis; laparoscopy remains the procedure of choice.