Wound healing is a complex biologic process that involves chemotaxis and division of cells, neovascularization, synthesis of extracellular matrix proteins, and remodeling of scar. Peptide growth factors have been shown to regulate many of these processes in vitro, leading to the hypothesis that peptide growth factors also regulate important phases of wound healing in vivo. Part I of this two-part series presents an overview of the biochemical properties of five families of peptide growth factors that are thought to be involved in wound healing: epidermal growth factor (EGF), transforming growth factor-beta (TGF-beta), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), and fibroblast growth factor (FGF).