We have investigated the regulation of translation during the period of rapid liver growth that occurs at the end of gestation in the rat. This work was based on our prior observation that fetal hepatocyte proliferation is resistant to the inhibitory effects of rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), a nutrient sensing kinase that controls ribosome biogenesis and protein translation. We hypothesized that translation control in late gestation fetal liver differs from that in adult liver. We first examined the ability of rapamycin to inhibit the translation of mRNAs encoding ribosomal proteins. Consistent with the effect of rapamycin on proliferation, the activation of adult liver 5'TOP translation that occurred during refeeding after food deprivation was sensitive to rapamycin. Fetal liver 5'TOP translation was insensitive. We went on to examine the eIF4F cap-binding complex, which controls global protein synthesis. The molecular weights of the multiple eIF4G1 isoforms present in fetal and adult liver eIF4F complexes differed. In addition, fetal liver expressed the eIF4A1 form of the eIF4A helicase while adult liver contained eIF4A1 and eIF4A2. Rapamycin administration prior to refeeding in adult rats inhibited formation of the pre-initiation complex to a much greater degree than rapamycin administration to fetal rats in situ. We conclude that there are major structural and functional differences in translation control between late gestation fetal and adult liver. These differences may confer differential sensitivity to the growth inhibitory effects of rapamycin.