NAT1 and NAT2 are two members of the N-acetyltransferases (NAT) family that encode polymorphic enzymes catalyzing the metabolic activation of heterocyclic aromatic amines (HCAs), which have been considered established carcinogens in human colorectal cancer and urinary bladder cancer (Kadlubar et al., 1992; Cross and Sinha, 2004). The gene discussed is NAT2; the disease is colorectal cancer.