Achondroplasia, the most common form of skeletal dysplasia in man, has autosomal dominant inheritance and causes severe dwarfism. More than 90% of patients with achondroplasia have a G to A transversion or G to C transversion at position 1138 of the fibroblast growth factor receptor-3 (FGFR3) gene resulting in the substitution of an arginine for a glycine residue at position 380 (G380R) of the FGFR3 protein. In this study, 12 unrelated Turkish patients with achondroplasia were evaluated for the G to A and G to C transversion at position 1138 of the FGFR3 gene. Eleven of 12 patients carried the G to A mutation heterozygously. None of the patients had the G to C mutation at the same position. In conclusion, the vast majority of Turkish achondroplasia patients have the same mutation that has been most often defined in patients with achondroplasia from other countries. Our results give further support to the fact that the G380R mutation of FGFR-3 is the most common mutation causing achondroplasia in different populations.