Objective To ascertain the histological characteristics of hereditary gingival fibromatosis and the location of HGF gene. Methods A pedigree analysis of HGF was made. The ultrastructure of gingival overgrown tissue was observed by electron microscopy (EMS) and the location of the HGF gene defined with microsatellite markers. Results The HGF consisted of coarse collagen bundles and fibrocytes, epithelial cells, smooth muscle cells, etc. were abnormally arranged; the HGF locus had been mapped to chromosome 5q13 q22. Conclusion The gingival pathological changes resemble “hamartoma” and the findings have implications for identification of the underlying genetic basis of HGF. Objective To ascertain the histological characteristics of hereditary gingival fibromatosis and the location of HGF gene. Methods A pedigree analysis of HGF was made. The ultrastructure of gingival overgrown tissue was observed by electron microscopy (EMS) and the location of the HGF Results The HGF consisted of coarse collagen bundles and fibrocytes, epithelial cells, smooth muscle cells, etc. were were only arranged; the HGF locus had been mapped to chromosome 5q13 q22. Conclusion The gingival pathological changes resemble “hamartoma ” and the findings have implications for identification of the underlying genetic basis of HGF.