To identify risk variants for childhood acute lymphoblastic leukemia (ALL) we conducted a genome-wide association study of 2 case-control series, analyzing the genotypes of 291,423 tagging SNP genotypes in a total of 907 ALL cases and 2,398 controls. We identified risk loci for ALL at 7p12.2 ( IKZF1, rs4132601; OR = 1.69, P = 1.20 x 10 -19), 10q21.2 ( ARIDB5, rs7089424; OR = 1.65, P = 6.69 x 10 -19) and 14q11.2 ( CEBPE, rs2239633; OR = 1.34, P = 2.88 x 10 -7). The 10q21.2 ( ARIDB5) risk association appears to be selective for the subset of B-cell precursor ALL with hyperdiploidy. These data show that common low-penetrance susceptibility alleles contribute to the risk of developing childhood ALL and provide novel insight into disease causation of this hematological cancer; notably all 3 risk variants map to genes involved in transcriptional regulation and differentiation of B-cell progenitors.