I have been privileged to witness and participate in the great growth of knowledge on chemical carcinogenesis and mutagenesis since 1939 when I entered graduate school in biochemistry at the University of Wisconsin Madison. I immediately started to work with the carcinogenic aminoazo dyes un der the direction of Professor CARL BAUMANN. In 1942 I joined a fellow graduate student, ELIZABE1H CAVERT, in marriage and we soon commenced a joyous part nership in research on chemical carcinogenesis at the McArdle Laboratory for Cancer Research in the University of Wisconsin Medical School in Madison. This collaboration lasted 45 years. I am very grateful that this volume is dedi cated to the memory of Elizabeth. The important and varied topics that are reviewed here attest to the continued growth of the fields of chemical car cinogenesis and mutagenesis, including their recent and fruitful union with viral oncology. I feel very optimistic about the application of knowledge in these fields to the eventual solution of numerous problems, including the detection and estimation of the risks to humans of environmental chemical carcinogens and re lated factors.