Fibroblast growth factors (FGFs) produce mitogenic and angiogenic effects in target cells by signaling through cell surface receptor tyrosine kinases. Each receptor contains an extracellular ligand binding domain, a transmembrane domain, and a cytoplasmic kinase domain. Following ligand binding and dimerization, the receptors are phosphorylated at specific tyrosine residues. Seven tyrosine residues in the cytoplasmic tail of FGFR1 can be phosphorylated: Tyr463, 583, 585, 653, 654, 730, and 766.