This article is a report on a symposium sponsored by the American Society for Pharmacology and Experimental Therapeutics presented at the joint meeting of the American Society for Biochemistry and Molecular Biology and the American Society for Pharmacology and Experimental Therapeutics, June 4-8, Boston, Massachusetts. The presentations focused on the pharmacogenetics of the NAT1 and NAT2 arylamine N-acetyltransferases, including developmental regulation, structure-function relationships, and their possible role in susceptibility to breast, colon, and pancreatic cancers. The symposium honored Wendell W. Weber for over 35 years of leadership and scientific advancement in pharmacogenetics and was highlighted by his overview of the historical development of the field.