A 6-year-old boy who hall been in remission from acute lymphoblastic leukemia for 2.5 years presented with seizures, hemiparesis, visual loss, and white- and gray-matter lesions oil cranial magnetic resonance imaging. The diagnosis of progressive multifocal leukoencephalopathy was established oil the detection of JC virus DNA by polymerase chain reaction in brain tissue. The patient was administered several anticonvulsants, amantadine, acyclovir, and ganciclovir. He showed partial recovery. This case illustrates the possibility of long-term survival in progressive multifocal leukoencephalopathy with normal immunologic parameters.