Objective To investigate the function of EM>Fin/EM>15 in mouse tooth development. Methods The expression of EM>Fin/EM> in mouse tooth germ was detected by RT-PCR. The expression of a fibroblast growth factor(FGF), inducible gene Fin15 in the early mouse dveloping tooth was detected by EM>in situ/EM> hybridization and EM>Fin/EM>15 expression in mouse mandible arch which was disrupted FGF singaling was examined by whole mount EM>in situ/EM> hybridization. Results EM>Fin/EM>15 was expressed in the both dental epithelium and mesenchyme from the initiation stage to the morphogenesis stage. Disruption of FGF signaling in mandible arch in organ culture abolished EM>Fin/EM>15 expression in the mandible, including tooth forming regions. Conclusion EM>Fin/EM>15 was a downstream target of FGF signaling pathway in developing tooth, implicating a role for EM>Fin/EM>15 in mediating function of FGF signaling in mammalian tooth