PURPOSE: To evaluate MR imaging findings of degenerating parenchymal neurocysticercosis and to determine the characteristics which distinguish it from other brain diseases. METHODS: MR imagings of 19 patients (56 lesions)of degenerating parenchymal neurocysticercosis were retrospectively evaluated, focusing on the size and locationof lesions, signal intensity patterns of cyst fluid and wall, the extent of the surrounding edema and features of contrast enhancement. RESULTS: Degenerating parenchymal neurocysticercosis was located in gray or subcortical white matter in 89.3% of 56 lesions(50/56); most of these (98.2%) were smaller than 2cm in diameter. Cyst fluidsignal was hyperintense relative to CSF on T1 and proton density weighted images (92.9%). A hypointense signal rimof the cyst wall was noted in the lesions on proton density (92.9%) and T2 weighted (98.2%) images. Surrounding edema was mostly mild. Peripheral rim enhancement was noted in all lesions, and this was frequently irregular and lobulated (67.9%) with a focal defect in the enhancing rim (41.1%). CONCLUSION: Findings which could be helpfulin distinguishing degenerating parencymal neurocysticerosis from other brain diseases are as follows : small, superficial lesions ; hyperintense signal of the cyst fluid on T1 and proton density weighted images ; hypointense signal of the cyst wall on proton density and T2 weighted images ; relatively mild extent of surrounding edema,and peripheral rim enhancement which is frequently irregular and lobulated with a focal defect in the enhancingrim.