Fifteen 7-16-year-old patients, treated in 1981-1984 for acute lymphoblastic leukemia (ALL) in first complete remission, were studied. As a central nervous system prophylaxis, all the children were treated with repeated methotrexate (MTX) instillations, but none were irradiated. The study protocol included magnetic resonance (MR) and a battery of neuropsychological tests. Small, punctate white-matter lesions were found by MR in eight children, probably minor vascular lesions. All the children were within normal intelligence range with a mean total WISC-R IQ of 109. Minor neuropsychologic problems were found in two patients, while one child showed a more extensive specific learning disorder in school.