OBJECTIVE We performed this study to compare contrast-enhanced fast multiplanar spoiled gradient-recalled (SPGR) MR imaging with unenhanced spin-echo imaging for the detection of benign and malignant peritoneal abnormalities. METHODS We retrospectively reviewed abdominal MR images of 34 patients with proved peritoneal abnormalities, including 21 patients with malignant and 13 patients with benign peritoneal disease. Six additional patients had false-positive interpretations of their MR examinations because of diaphragmatic thickening and enhancement. Unenhanced T1-weighted images, fast spin-echo T2-weighted images, and breath-hold fast multiplanar SPGR images obtained immediately and 10-15 min after IV injection of gadopentetate dimeglumine were available. Images were reviewed for evidence of peritoneal disease by two observers who had no knowledge of the clinical findings. The four types of images were separately evaluated for peritoneal thickening, masses, and abnormal enhancement. The anatomic location, thickness, and pattern of thickening of the peritoneum were noted. Results were correlated with surgical findings or results of percutaneous biopsy. RESULTS Immediate and delayed contrast-enhanced fast multiplanar SPGR images showed malignant peritoneal tumor in all 21 cases, compared with T1-weighted images, which showed tumor in 11 cases (p < .01), and fast spin-echo T2-weighted images, which showed tumor in 13 cases (p < .01). Enhancement of the peritoneal tumor increased the tumor's conspicuity, particularly on delayed fast multiplanar SPGR images, which were selected as the best sequence for detection of peritoneal tumor in 18 of the 21 cases. The MR findings varied widely from moderately and regularly thickened, enhancing peritoneum to very thick (> 1 cm) and lobular or masslike peritoneal thickening with enhancement. Delayed fast multiplanar SPGR images showed evidence of benign peritoneal disease in all 13 cases compared with immediate fast multiplanar SPGR images, which showed disease in 12 cases (p > .05); T1-weighted images, which showed disease in four cases (p < .05); and fast spin-echo T2-weighted images, which showed disease in only one case (p < .01). In the benign forms of peritoneal disease, the peritoneum was often regular in contour and tended to be thinner than in the cases of malignant peritoneal tumor, in which the peritoneum was generally thicker and more lobular or masslike. However, significant overlap was seen between the MR findings in benign and malignant forms of peritoneal disease. CONCLUSIONS Detection of peritoneal abnormalities with MR imaging can be improved by using contrast-enhanced fast multiplanar SPGR imaging. The findings of peritoneal thickening and enhancement are best depicted on delayed images.