Meticulous pretreatment evaluation is basic to the successful management of suspected ovarian masses. Among currently available imaging techniques, sonography and computerized tomography are the most important diagnostic modalities. The purpose of our study was to determine whether magnetic resonance imaging provided additional information on masses in the true pelvis. 73 patients with masses in the true pelvis underwent preoperative magnetic resonance imaging. MRI was done with a 1.0 T supraconductive magnet (Magnetom Impact, Siemens). The results obtained were compared with sonographic (transabdominal and transvaginal), intraoperative and histopathologic findings. MR images were evaluated for their information on differentiation between benign and malignant neoplasm, tumor staging, lymph node involvement, peritoneal spread, local extension and organ relation. MRI correctly characterized malignant and benign tumors in 97% of cases versus 81% on ultrasound. The site of the primary tumor was correctly diagnosed in 94% of cases on MRI images versus 86% on ultrasound images. Invasion of adjacent intestinal segments as well as peritoneal carcinomatosis and omental metastases (metastasis > 1 cm) were also detected in the majority of cases. Based on our results MRI performs well at lesion detection and characterization in the evaluation of suspected ovarian masses. MRI should be considered in the investigation of patients with complicated findings on ultrasound.