A series of protocols has been assembled and used for the assessment of implantation failure following chemical exposure in the rat. Upon detecting a chemically-induced blockade of implantation, these protocols are designed to probe the physiological mechanisms through which the chemical may impair early pregnancy, including a distinction between embryotoxicity and maternal reproductive toxicity. The protocols include the early pregnancy protocol, the decidual cell response technique, the pre-vs. postimplantation protocol, and the embryo transport rate analysis. These protocols are simple and rapid and provide considerable information regarding the effects of chemicals on the processes involved during embryo implantation.