This text brings together the work of several investigators who used in vitro techniques to probe the nature of embryonic cell response to a diverse group of chemical agents. It focuses on the approaches, limitations, usefulness and applicability of defining mechanisms underlying altered development. This work includes discussions on pharmacodynamic principles and placental transfer mechanisms. It also examines the potential for in vitro systems to serve as an adjunct to the risk assessment process. Ideal for both the layman and the expert in this area, this volume provides a general understanding of the types of approaches that can be used and specific approaches in investigating altered development.