The radionuclide, radiographic and pathologic findings in a patient with progressive multifocal leukoencephalopathy were correlated. Radionuclide imaging demonstrated the largest two of the many lesions observed at pathology. On repeated studies, one of the lesions developed a "doughnut" sign due to central necrosis. Cerebral angiography disclosed only one lesion which was initially suggestive of tumor encasement, but four weeks later, this deteriorated into an avascular zone. There were no characteristic features of the lesions demonstrated by radionuclide imaging and cerebral angiography that could be specifically attributed to progressive multifocal leukoencephalopathy.