It has been over 40 years since the original report by Salmon and Daughaday demonstrating that the ability of GH to stimulate sulfation of cartilage was mediated by a sulfation factor. In the ensuing decades, it has become apparent that this sulfation factor activity encompasses a complex system of ligands (IGFs), receptors, and carrier proteins that are, in turn, responsible for a wide array of cellular actions. The IGF system has been demonstrated to be critically involved in both intrauterine and postnatal growth, and to have important implications in cancer biology as well, owing to the ability of the IGFs to function in endocrine, paracrine, and autocrine modes and given the wide distribution of IGFs in virtually every organ system. The contributions to the IGF system reflect the wide span of interest in the IGF system and its implications for normal and abnormal growth.