Fibroblast growth factors (FGFs) are a family of small, glycosylated intercellular signaling proteins. The human genome contains 29 potential *FGF* genes, with transcripts identified for 23 of them. FGFs signal through a family of four transmembrane receptor tyrosine kinases, which require a sulphated glycosaminoglycan (GAG) co-factor for activation. Signal transduction activates multiple pathways, including the Ras/MAP kinase pathway, PI 3-kinase pathway, and inositol lipid/calcium pathway. Feedback regulation involves tyrosine phosphatases, Sef proteins, and Sprouty proteins. Alternative splicing of FGF receptor RNAs affects ligand specificity and receptor function. FGFs are involved in various cellular responses, including proliferation, apoptosis, differentiation, and chemotaxis. Clinically, they are potent oncogenic and angiogenic agents, and mutations in FGF receptors underlie several syndromes. Developmentally, FGFs are crucial for processes such as mesoderm and neural induction, limb outgrowth, and regional patterning of the brain. While FGFs are mitogens for many transformed fibroblast cell lines, they do not affect primary fibroblasts.Fibroblast growth factors (FGFs) are a family of small, glycosylated intercellular signaling proteins. The human genome contains 29 potential *FGF* genes, with transcripts identified for 23 of them. FGFs signal through a family of four transmembrane receptor tyrosine kinases, which require a sulphated glycosaminoglycan (GAG) co-factor for activation. Signal transduction activates multiple pathways, including the Ras/MAP kinase pathway, PI 3-kinase pathway, and inositol lipid/calcium pathway. Feedback regulation involves tyrosine phosphatases, Sef proteins, and Sprouty proteins. Alternative splicing of FGF receptor RNAs affects ligand specificity and receptor function. FGFs are involved in various cellular responses, including proliferation, apoptosis, differentiation, and chemotaxis. Clinically, they are potent oncogenic and angiogenic agents, and mutations in FGF receptors underlie several syndromes. Developmentally, FGFs are crucial for processes such as mesoderm and neural induction, limb outgrowth, and regional patterning of the brain. While FGFs are mitogens for many transformed fibroblast cell lines, they do not affect primary fibroblasts.