The neurotoxicity of either systemic chemotherapy or central nervous system prophylaxis was studied in 19 children treated for acute lymphoblastic leukemia (ALL). They had completed ALL therapy at least a year before and survived more than 5 years after diagnosis. The duration between age at diagnosis and age at investigation was 8.6 +/- 2.7 years (5-15 years). Neuropsychologic tests, cranial magnetic resonance imaging (MRI), and evoked potentials (EP) were studied. Seventeen healthy siblings were taken as a control group. Emotional evaluation was done using the childhood depression inventory and Beck depression inventory. Cognitive functions were evaluated using Wechsler's Intelligence Scale for Children-Revised (WISC-R) or the Wechsler's Adult Intelligence Scale-Revised (WAIS-R) tests, which were adapted to Turkish children. Performance and total IQ scores (94.0 +/- 16.8 and 92.2 +/- 16.5) were significantly low as compared to the control group (112.1 +/- 18.9 and 105.4 +/- 14.2) (p = .007 and p = .02). Abnormal MRI findings were found in 33.3% (6/18). Three out of 18 patients (16.6%) had abnormal auditory while 5 out of 17 patients (29.5%) displayed abnormal visual EPs. Abnormal findings in MRI, cognitive examination, and electrophysiologic testing were not associated with age at diagnosis, radiotherapy doses, intermediate/high-dose systemic methotrexate administration or central nervous system involvement. But more patients must be studied to demonstrate discrete outcomes of neurotoxicity in long-term survivors of childhood leukemia.