Gefitinib inhibits epidermal growth factor-independent angiogenesis, but the molecular mechanism underlying this inhibition has yet to be defined. Here we show that gefitinib dose-dependently inhibited chemotaxis of endothelial cells toward fibroblast growth factor-2 (FGF-2), but not toward vascular endothelial growth factor-A (VEGF-A). Gefitinib inhibited lamellipodium formation by endothelial cells induced by FGF-2, but not by VEGF-A. Gefitinib at 10 microM did not inhibit autophosphorylation of FGF receptor 1 or VEGF receptor 2. A non-receptor protein tyrosine kinase, Fes, has two coiled-coil domains (CCDs) in its N-terminal region. Fes is activated by trans-autophosphorylation through CCD functions. An inactivating mutation in the second CCD abolished FGF-2 activation of Fes, indicating involvement of this CCD in FGF-2-induced Fes activation. Gefitinib-treatment decreased both CCD-independent and FGF-2- or VEGF-A-promoted Fes activity with a maximal decrease at 1 microM. The same results were observed in cells stably expressing kinase-inactive Fes; a dominant negative effect was observed in cells treated with FGF-2, but not with VEGF-A. Taken together, these results indicate that FGF-2 activates Fes via the second CCD, leading to lamellipodium formation and chemotaxis by endothelial cells, and gefitinib may act through Fes as an inhibitor of FGF-2-driven angiogenesis.