Heparin-binding EGF-like growth factor (HB-EGF) is a 22 kDa, O-glycosylated protein that is mitogenic for fibroblasts, smooth muscle cells (SMC) and epithelial cells. This review describes the primary structure of HB-EGF, as well as its processing. The structure of the mouse and human HB-EGF genes is also discussed. Finally, this review summarizes HB-EGF expression patterns, receptor-mediated signaling, and role in several important biological systems.