The detection of cancer risk factors and their possible avoid- ance would most effectively contribute to the fight against cancer. Research in these areas depends to a substantial degree on in vivo experimental animal models and on epide- miologic studies, including data from cancer registries. When the Deutsches Krebsforschungszentrum was founded in 1964, its division "Mechanisms of Tumorigenesis" and a number of other divisions became engaged in research on chemical carcinogenesis of the skin, mainly using the mouse skin as an experimental model. Their interest orig- inated in part from...