This detailed background review paper provides a summary of the relevant literature (up to September 2001) relevant to the standardisation and validation of the rodent uterotrophic bioassay. The rodent uterotrophic bioassay is being validated as part of the OECD Test Guidelines Programme.  The rodent uterotrophic bioassay is based on the principle that the uterus is under the control of oestrogens to stimulate and maintain growth. If endogenous sources of this hormone are not available, the
animal will require an exogenous source to initiate and/or restore uterine growth.