Acidic and basic fibroblast growth factors (FGFs) are members of a family of multifunctional polypeptide growth factors that stimulate proliferation of cells of mesenchymal, epithelial and neuro-ectodermal origin. Like other growth factors, FGFs act by binding and activating specific cell surface receptors. A total of six members of the FGF receptor family have been identified and cloned. These include the Flg receptor or FGFR-1, the BEK receptor or FGFR-2, FGFR-3, FGFR-4, FGFR-5 and FGFR-6. These receptors usually contain an extracellular ligand-binding region containing three immunoglobulin-like domains, a transmembrane domain and a cytoplasmic tyrosine kinase domain. However, FGFR-5 lacks the cytoplasmic kinase domain. FGFR-5 is expressed in a broad range of tissues, including kidney, brain and lung, but it is preferentially expressed in pancreas, where it may play a role in the regulation of some pancreatic function.