The insulin-like growth factor II (IGF-II) is involved in embryonic growth. Modifications of its expression might play a role in the development of primary liver cancer in humans and woodchucks. In the liver, little information is available on the cell types involved in its synthesis. We have investigated the expression of IGF-II as well as IGF-II, IGF-I and insulin receptor mRNAs in non parenchymal liver cell preparations in rats of various ages. The results indicate that Kupffer cells, endothelial cells and fat-storing cells express both IGF-II and the three different receptor mRNAs. Furthermore, a switch from a fetal to an adult IGF-II mRNA profile was obtained in the different cell preparations. Therefore, our results indicate that regulation of IGF-II gene expression can be analyzed through these isolated liver cell preparations. These results might also be important in investigating the potential role of IGF-II in liver carcinogenesis.