The aim of this publication is to introduce newcomers in this field to transgenic mutagenicity assays and to assess the possible role of these assays in toxicology testing and mechanistic research. Part I gives a short overview of in vivo genotoxicity testing. Part II gives an overview of the data produced by various assays. Part III discusses the use of the assays in research. Part IV evaluates the role and potential added value of transgenic mutation assays in toxicology and risk assessment. The book is directed at toxicologists, research scientists, and risk assessors.