IGF-II is a member of the IGF family that is comprised of three members (IGF-I, IGF-II, and insulin). IGF-I and IGF-II share approximately 50% similarity with insulin at the amino acid level. IGF-II is synthesized as a 180 amino acid in the pro-IGF-II form; pro-IGF-II is processed to the mature, active protein with the help of glucose regulating protein 94 (GRP94) that possesses chaperone activity towards IGF-II. GRP94 and IGF-II play a key role in muscle differentiation. Seven binding proteins have been described (IGFBP-1 to -7). IGFBPs extend the half life and regulate the availability of the IGFI and IGFII. It has been described that IGFBP3 is the main circulating binding protein for IGFs; in serum approximately 75% of circulating IGF-I and IGF-II bind to IGFBP3 and the co-carrier acid labile subunit (ALS). IGF-II binds to three receptors, and the binding to IGFIR promotes cell proliferation, survival, differentiation, and migration as well as metabolic function of IGF-II. Embryonic stem cell differentiation into endothelial cells is promoted by the binding of IGF-II to IGFR1. IGF-II binding to IGF-IIR induces internalization and clearing of IGF-II. Osteogenic differentiation and bone formation is enhanced by IGF-II through bone morphogenetic protein-9 (BMP-9). Polymorphisms of IGF-II are associated with obesity, cardiovascular risk factors, and hypertension.