A kindred affected with hereditary fibrous hyperplasia of the gingiva with varying penetrance and expressivity is described. Most of the affected members were short in stature. The pedigree strongly suggested an autosomal dominant mode of inheritance. The penetrance of the trait varied, and three unaffected persons had transmitted the disease to their offspring. There were two modes of expression. The mild form showed only bilateral rugose thickening of the palate, whereas the severe form showed gingival hyperplasia in addition to changes in the palatal mucosa. The changes were already present at birth. Histological examination showed large amounts of alcian blue-positive extracellular material in the subepithelial connective tissue of the hyperplastic mucosa. Loose collagen-poor connective tissue with alcian blue-positive extracellular material and dense collagen-rich connective tissue in the rugose projections of the palatal mucosa were often segregated.