The predicted haplotypes described as slow acetylator TCTGAG (NAT2*5V, CI 1.39–201.58) and rapid CTTGAG (NAT2*11A, CI 2.05–348.8) and CTTGGG (NAT2*12C, CI 1.32–36.83) haplotypes, which were rare in the healthy subjects (<1%), were associated with higher risk of ALL. The gene discussed is NAT2; the disease is acute lymphoblastic leukemia.