Regulators at a 2003 ILSI-HESI workshop on the use of transgenic animals for carcinogenicity testing concluded that these assays should be integrated with traditional test methods (ILSI-HESI, 2003). The regulators considered the p53+/- and Tg. RasH2 models useful in providing data for regulatory purposes and the Tg. AC model useful in evaluating dermal products.