Fibroblast growth factor-8 (Fgf8) is a recently identified growth factor that stimulates the androgen-dependent growth of mouse mammary carcinoma cells. Evidence from mouse development also shows that Fgf8 may play an important role in growth and patterning of limbs, face, and the central nervous system. We describe here the human FGF8 genomic sequence and demonstrate conservation between the human and mouse sequences, including alternatively spliced exons in the mouse. Mapping of FGF8 by FISH using an FGF8-containing bacterial artificial chromosome and by genetic linkage using a SSCP variant identified in this study is also reported and refines the FGF8 map location to 10q24. Since FGF8 maps to the same chromosomal region as FGFR2, has indeed been shown to be a ligand for FGFR2, and has an expression pattern consistent with limb and craniofacial anomalies, we have screened two kindreds with Pfeiffer syndrome that were previously linked to markers from 10q24-25 and a large number of individuals with craniosynostosis and limb anomalies for mutations in the coding sequence of FGF8. While no such mutations were identified, a rare polymorphic variant, consisting of an 18-base-pair (six-amino-acid) duplication in exon 1c, is reported that apparently has no clinical effect. Our exclusionary data suggest that mutations in FGF8 would be, at best, an infrequent cause of such disorders.