Changes in consensus arylamine N-acetyltransferase (NAT) gene nomenclature determined at the 2007 International NAT Workshop include: (1) Alleles in all species except mouse and rat are all uppercase. For mouse and rat, the first letter is upper case followed by lower case. (2) The nomenclature system is now species-specific. Thus, NAT2(*)1 (chicken), NAT2(*)2 and NAT2(*)3 (rabbit), Nat2(*)8 Nat2(*)9, Nat2(*)22 and Nat2(*)23 (mouse), NAT2(*)15, NAT2(*)16A and NAT2(*)16B (Syrian hamster), and NAT2(*)20, NAT2(*)21A and NAT2(*)21B (rat) are retired and renumbered within a species. A species modifier incorporated into the allele designation is written in upper case Roman font, e.g., (MOUSE)Nat1(*)1 is now the reference Nat1 allele in mouse; and (3) The NAT website also can now be accessed at a webalias address: http://N-acetyltransferasenomenclature.louisville.edu. New NAT alleles should continue to be submitted to the NAT Nomenclature Committee for inclusion on the website to ensure proper categorization and to continue consistency in nomenclature.