Our aim was to address the hypothesis that maternal dietary intake of folate during pregnancy is inversely associated with risk of acute lymphoblastic leukemia (ALL) in the offspring. Dietary intake of folate, vitamins B6 and B12 in the last 6 mo of pregnancy from 333 cases and 695 frequency-matched controls were assessed using a food frequency questionnaire. Data were analyzed using unconditional logistic regression, adjusting for study matching variables, total energy, and potentially confounding variables. Higher levels of dietary folate and B12 appeared to be associated with a decreased risk of ALL. Higher levels of vitamin B6 were associated with an increased risk. The strongest associations of ALL with these variables were seen when mothers consumed alcohol in pregnancy. Our findings are consistent with a modest protective effect of higher dietary intake of folate and vitamin B12 against ALL in the offspring, more particularly among women who drank alcohol during pregnancy. These findings are consistent with previous reports of the protective effects of a maternal diet high in fruit, vegetables, and nondairy protein sources. The vitamin B6 findings are not consistent with evidence that it is a protective factor against other cancers, and may be a chance finding.