Approximately 10% of children treated with contemporary therapy for acute lymphoblastic leukemia (ALL) will experience an isolated relapse in the central nervous system (CNS). From 5 to 25% of this group will become long-term survivors, but only after additional, more aggressive therapy. A review of the limited number of studies of children surviving treatment for CNS relapse disclosed a strikingly higher incidence of intellectual impairment than was found in similarly treated patients who remain in complete remission. Specific risk factors for this complication included the number of courses of cranial irradiation, a young age at treatment, increasing time since treatment, neuropathological changes apparent on abnormal computed tomography scans of the brain, and seizures. The methodological problems inherent in neurobehavioral research in childhood acute lymphoblastic leukemia are critically reviewed and suggestions for future studies are offered. Children with a CNS relapse should be serially evaluated for psychoeducational performance to facilitate early intervention in cases of learning difficulties.