PURPOSE: The purpose of this study is to describe the characteristic features of cerebral sparganosis with live worm on CT and MRI as compared with the characteristic CT and MRI features of degenerated cerebral worms. MATERIALS AND METHODS: Twelve patients with surgically-proven live worms (the live group) and 13 patients with degenerated worms (the degenerated group) were included in this study. We retrospectively reviewed the CT scans of all the patients and the MR images of 19 patients. RESULTS: The live group showed highly attenuated lesion (50-70 HUs for the CT number) on precontrast CT with surrounding enhancement extending to the cortical surface, a mass effect and change of the location and shape of the enhancing lesion on the follow-up images, whereas the degenerated group showed punctate calcification (more than 130 HUs) with surrounding enhancement and cerebromalacia in 77% of the subjects (p<.01). The highly attenuated lesion had an amorphous nodular or nodulotubular shape, and these lesions were slightly hyperintense on the T1-weighted MR images and hypointense on the T2-weighted MR images. CONCLUSION: In patients with cerebral sparganosis, live worm infection is highly suggested if there is a focal amorphous hyperattenuated lesion on the precontrast CT with a surrounding mass effect, irregular nodulotubular enhancement extending to the pial surface and change of the enhancing lesion on the follow-up images.