Retinyl palmitate (all-trans-retinyl palmitate; RP) was nominated in 2001 by the U.S. Food and Drug Administration’s Center for Food Safety and Applied Nutrition (CFSAN) to the National Toxicology Program (NTP) as a high priority compound for phototoxicity and photocarcinogenicity studies at the National Center for Toxicological Research (NCTR). Studies with SKH-1 hairless mice are required to test whether topical application of RP enhances the phototoxicity and photocarcinogenicity of simulated solar light and UV light. Mechanistic studies are needed to provide insight into the disposition of RP in vitro and on the skin of mice, and to test thoroughly whether genotoxic damage by UV-induced radicals may participate in any toxicity of topically applied RP in the presence of UV light.