The Fibroblast Growth Factors (FGFs) are heparin binding glycoproteins that exert a variety of biological activities toward cells of mesenchymal, neuronal, and epithelial origin. FGF-10 belongs to the subgroup of FGFs that also includes FGF-3, -7, and -22. Mature human FGF-10 is an approximately 20 kDa protein that contains a serine-rich region near its N-terminus. It shares 93% and 96% amino acid sequence identity with mouse and rat FGF-10, respectively. FGF-10 is secreted by mesenchymal cells and associates with?extracellular FGF-BP. It preferentially binds and activates epithelial cell FGF?R2 (IIIb) and interacts more weakly with FGF?R1 (IIIb). The mitogenic and chemotactic properties of FGF-10 are critical in many tissues during embryogenesis. This includes limb bud initiation, palate development, branching morphogenesis and directional outgrowth of lung buds, formation of the otic vesicle and chochlea, adipogenesis, and the development of prostate, mammary, lacrimal, and submandibular salivary glands. FGF R2 (IIIb) signaling in these responsive tissues is similarly important during embryogenesis. The expression and function of FGF-10 are negatively regulated by Shh and BMP-4 in the developing lung. Overlapping expression patterns and activities with FGF-3, -7,?and -8 suggest at least a partial redundancy in FGF?10 biology. FGF-10 induced signaling through FGF R2 (IIIb) also contributes to the progression of pancreatic cancer.