Hereditary Gingival Fibromatosis (HGF) is a rare, benign disorder characterized by slowly progressive fibrous overgrowth of the gingiva. HGF occurs in several forms as a Mendelian trait (usually as an autosomal dominant condition), in malformation syndromes, in chromosomal abnormality syndromes and side effect of several pharmacological agents. Except Son of sevenless-1 (SOS1) gene mutation, molecular basis of HGF is unclear. Here, we reported the cytogenetic and SOS1 gene mutation analysis in a Turkish family with 7 affected members through three generations, whose features are consistent with the diagnosis of autosomal dominant, isolated hereditary gingival fibromatosis. To the best of our knowledge this is the first large Turkish family with hereditary gingival fibromatosis. In this study, we excluded the chromosomal abnormalities and the mutation in SOS1 gene at this family. © 2009 The Hard Tissue Biology Network Association.