Six mouse size categories, and four rat sizes were analysed. Vitamin E concentration was similar among all mice classes (mean = 43.8 +/- 13.4 IU/kg dry). Rat pinkies contained 470.4 +/- 158.7 IU/kg dry while older rat size classes did not differ (mean = 138.0 +/- 67.2 IU/kg dry). Vitamin A concentrations increased with age in both mice and rats, from approximately 16,700 IU/kg (crawler mice) to approximately 300,000 IU/kg in adults (dry matter basis). Fuzzy and crawler mice did not differ nutritionally; proximate composition in mice was similar to previously reported data for rodents. Rat proximate composition did not differ among any size category (13% ash, 28% crude fat, 56% crude protein), except water decreased with age (79-65%).