Comparison of paediatric leukaemias with and without ALL-1 rearrangement indicated significant bias in the former for NQO1 genotypes conferring low or no enzymatic activity (Wiemels et al, 1999; Smith et al, 2002), suggesting that inactivating NQO1 polymorphism increases the risk for ALL-1-associated leukaemias. The gene discussed is NQO1; the disease is leukemia.