The aim of this study was to conduct clinical, genetic, and molecular analysis of Chinese patients with granular corneal dystrophy type I (CDGG1). Two large unrelated Chinese families with CDGG1 were clinically and genetically evaluated. Molecular genetic analysis was performed on DNA extracted from peripheral blood. Exons 4, 11, 12, and 14 of the human transforming growth factor beta-induced gene (TGFBI, formerly designated BIGH3) were amplified by PCR, scanned for mutations using the single-strand conformation polymorphism method, and the mutations identified by nucleotide sequencing. One family segregated the p.Ala546 > Asp mutation, and the other family had a p.Arg555 > Trp mutation. These missense mutations were not found in 53 unrelated, healthy individuals analyzed as controls. Clinical and genetic evaluations revealed the variable severity, symmetry, and age of onset in visual impairment in these families for different mutations. Penetrance of visual impairment in these families was 100% and 75%, respectively. This study confirms that the p.Arg555 > Trp mutation is a frequent cause of CDGG1, and that the p.Ala546 > Asp mutation is also associated with this disease.