Pfeifter syndrome (PS) is an autosomal dominant skeletal disorder which affects the bones of the skull, hands and feet. Previously, we have mapped PS in a subset of families to chromosome 8cen by linkage analysis and demonstrated a common mutation in the fibroblast growth factor receptor-1 (FGFR1) gene in the linked families. Here we report a second locus for PS on chromosome 10q25, and present evidence that mutations in the fibroblast growth factor receptor-2 (FGFR2) gene on 10q25 cause PS in an additional subset of familial and sporadic cases. Three different point mutations in FGFR2, which alter the same acceptor splice site of exon B, were observed in both sporadic and familial PS. In addition, a T to C transition in exon B predicting a cysteine to arginine substitution was identified in three sporadic PS individuals. Interestingly, this T to C change is identical to a mutation in FGFR2 previously reported in Crouzon syndrome, a phenotypically similar disorder but one lacking the hand and foot anomalies seen in PS. Our results highlight the genetic heterogeneity in PS and suggest that the molecular data will be an important complement to the clinical phenotype in defining craniosynostosis syndromes. / 1995 Oxford University Press.