The ready acceptance and wide demand for copies of the first two volumes of Chemical Mutagens: Principles and Methods Jar Their Detection have demon­ strated the need for wider dissemination of information on this timely and urgent subject. Therefore, it was imperative that a third volume be prepared to include more detailed discussions on techniques of some of the methods that were presented from a theoretical point of view in the first two volumes, and to update this rapidly expanding field with current findings and the new developments that have taken place in the past three years. Also included is a special chapter by Dr. Charlotte Auerbach giving the historical background of the discovery of chemical mutagenesis. Methods for recognizing mutagenic compounds in vitro are a necessary preliminary step toward arriving at satisfactory solutions for recognizing significant mutation rates in man, which must be done before our test­ tube methods of detection can be considered reliable. Two chapters in this volume make important contributions to this problem. Due to the increasing activity in efforts to perfect techniques for detecting chemical mutagens and their effects on man, it is planned to continue this series of volumes as necessary to keep abreast of current findings.