In addition to its well-known effects on metabolism, insulin stimulate the growth and proliferation of a variety of cells in culture, and evidence suggests that insulin may also be an important regulator of growth in vivo. The growth-promoting effects of insulin appear to be mediated by its own receptors, but in some cells, insulin appears to stimulate growth at high concentrations by activating insulin-like growth factor Ⅰ(IGF-Ⅰ) receptors. The post-receptor signal transduction consists of a series of receptor-associated tyrosine protein kinase activated intracellular protein phosphorylation and dephosphorylation reactions, such as the phosphorylation of insulin receptor substrate-1(IRS-1), Shc, Ras and phosphatidylinositol 3-kinase (PI3-K). It is supposed that some regions or sites on the insulin molecule may contribute more to the growth-promoting effects, and some preliminary evidences have come from the studies on several high mitogentic potent insulin analogues.