BACKGROUND: Although previous research has delineated medical, cognitive, and neuropsychologic late effects of central nervous system (CNS) prophylaxis for childhood acute lymphoblastic leukemia (ALL), it has been difficult to draw conclusions about the long term psychosocial sequelae of these treatments due to methodologic problems that led to inconclusive results in past studies. In the current study, the authors examined the long term psychosocial functioning of childhood ALL survivors who had been treated on a Phase III clinical protocol (Cancer and Leukemia Group B [CALGB] 7611) between 1976 and 1979, in which they were randomized to receive either 2400 centigray of cranial radiation (CRT) with intrathecal methotrexate (IT-MTX) or intermediate dose systemic methotrexate (IV-MTX) with IT-MTX. METHODS: One hundred ten survivors of childhood ALL (mean age, 20.8 years) treated on CALGB 7611 who were age 14 years or older and disease free for at least 1 year were studied a mean of 14.7 years after their entry on CALGB 7611. In a telephone interview, a psychosocial assessment battery was administered to the patients, consisting of measures that assessed psychologic, sexual, social, and vocational functioning as well as any delayed physical effects. RESULTS: Survivors who had received CRT + IT-MTX had significantly poorer academic achievement (P = 0.0001), poorer self-images with regard to their bodies (P = 0.001), and greater psychologic distress (P = 0.005). CONCLUSIONS: Cranial radiation used to treat children with ALL has significant long term sequelae in terms of poorer academic achievement and psychosocial functioning. These data add weight to the conclusion that CRT prophylaxis should only be used to treat children who are at high risk of CNS relapse.