Encephalopathy, leukoencephalopathy, and secondary parkinsonism occurred in 3 children with refractory leukemia undergoing allogenic bone marrow transplantation (BMT) who were treated with high-dose amphotericin B for pulmonary aspergillosis or sinus aspergillosis that did not involve the nervous system. Treatment included high-dose cytosine arabinoside, cyclophosphamide, and total body irradiation prior to the BMT. The children developed a progressively worsening encephalopathy and parkinsonian features, characterized by resting tremor, cogwheel rigidity, and masklike facies. Neuroimaging studies showed cerebellar, cerebral, and basal ganglia atrophy, as well as frontal and temporal lobe white matter involvement. Two of the 3 patients recovered, although 1 has residual intellectual impairment. The third succumbed to non-central nervous system Epstein-Barr virus-lymphoproliferative disease and had autopsy-confirmed leukoenephalopathy.