To describe the morphologic magnetic resonance imaging (MRI) findings in histologically proven therapy-induced cerebral necrosis. We retrospectively reviewed the morphologic MRI findings in patients with therapy-induced cerebral necrosis. Images were reviewed for size, location, and characteristics of signal intensity abnormalities and T1-contrast enhancement. Images were also assessed for mass effect, necrosis, cyst, atrophy, cortical thinning, and leukoencephalopathy. The individual imaging characteristics were correlated with clinical and treatment variables. There were 44 patients. Seventy percent had a glioma, all patients had received radiation, and 57% had received chemotherapy in close proximity to radiation. All images demonstrated contrast enhancement, predominantly in the white matter. Enhancement was present in the periventricular/subependymal region in 50% of cases and the corpus callosum in 27%. The most common pattern of lesion peripheral enhancement was "spreading wavefront" and of interior enhancement was "Swiss cheese/soap bubble." The enhancing lesion was single in 60% of cases. Mass effect was present in 93% of patients. Location and patterns of enhancement were significantly associated with the interval from brain radiation to the diagnosis of therapy-induced cerebral necrosis, tumor histology, patient age, type of radiation, and administration of systemic chemotherapy. This is the largest study of the morphologic conventional MRI findings in pathologically confirmed therapy-induced cerebral necrosis. We characterized the imaging findings in a variety of tumor types following a variety of radiation treatments and other antineoplastic therapy. These findings may be of value in identifying therapy-induced cerebral necrosis in patients treated for a brain tumor.