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, ELIZABETH CA VERT, 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.

Once again the Current Topics in Microbiology and Immunology series presents a volume with up-to-date review articles on oncogenes. The well-known authority and editor of previous volumes in the series, Dr. Vogt, has accepted five contributions which critically evaluate recent research in the field.

and how the known vertebrate homologues of these genes are expressed normally in differentiation and proliferation pathways as well as abnormal ly in well-defined lymphomagenic and other oncogenic pathways. What emerged from this meeting are a better understanding of the evolution of these gene systems themselves and an elucidation of simpler systems open to more rapid genetic and molecular genetic analysis to reveal the normal functions of these genes and their gene products. Thus we sought new answers to several old questions concerning differenti ation, proliferation, and neoplastic transformation. We gathered together in an unusual format - that of the unique Dahlem Workshops - not just to reiterate data which has recently emerged but to think about how these findings might lead to new approaches for the understanding and therapy of the leukemias and lymphomas. We deliberately chose experts from several different disciplines, ranging from the clinicians who diag nose, describe, and treat these maladies, to the molecular geneticists trying to reduce the analysis of the problem to its simplest variables in the simplest systems possible."