The murine homolog of the fibroblast growth factor-5 (FGF-5) gene has been cloned, and the sequence of the gene's three exons has been determined. The murine gene and the previously isolated human FGF-5 gene are substantially homologous within the coding sequences and in upstream sequences, which contain an additional open reading frame. We have used a portion of the murine gene as probe to detect FGF-5 RNA in adult mouse tissues by both Northern blot and in situ hybridization methods. FGF-5 RNA is present at low levels in widely distributed areas of the central nervous system. Several loci of FGF-5 expression could be localized by in situ hybridization and include portions of the cerebral cortex, hippocampus, and thalamus. Neuronal expression accounts for at least some of the FGF-5 RNA synthesized in the central nervous system.