Fibroblast growth factors are essential molecules for development. Here we characterize Fgf17, a new member of the fibroblast growth factor (FGF) family. The Fgf17 gene maps to mouse chromosome 14 and is highly conserved between mouse and human (93% identity). It exhibits 60% amino acid identity with Fgf8 and 50% identity with Fgf18. Both Fgf8 and Fgf17 have a similar structure and a similar pattern of alternative splicing in the 5′ coding region. When expressed in 3T3 fibroblasts, mouse FGF17 is transforming, indicating that it can activate the ‘c’ splice form of either FGF receptor (FGFR) one or two. During midgestation embryogenesis, in situ hybridization analysis localized Fgf17 expression to specific sites in the midline structures of the forebrain, the midbrain-hindbrain junction, the developing skeleton and in developing arteries. Comparison to Fgf8 revealed a striking similarity in expression patterns, especially in the central nervous system (CNS), suggesting that both genes may be important for CNS development, although Fgf17 is expressed somewhat later than Fgf8. In the developing skeleton, both genes are expressed in costal cartilage while Fgf8 is preferentially expressed in long bones. In the developing great vessels Fgf17 is preferentially expressed, suggesting that it may have a more prominent role in vascular growth.