Prion diseases compass transmissible spongiform neurodegenerative diseases from various causes, including the genetic and infectious ones. We investigated the prevalence of codon 117, 129 and 171 polymorphism in prion protein (PrP) in Taiwanese, mainly for the sake of the informative absence of this genetic distribution. Our subjects were 419 aged ones of Han ethic origin. We evaluated the PrP gene (PRNP) polymorphism by restriction fragment length polymorphism, after amplification of their genomic DNAs by polymerase chain reactions with specific primers, digested by restriction enzyme PvuII (for codon 117), NspI (for codon 129), and BbvI (for codon 171), respectively, and confirmed by nucleotide sequencing. All of the subjects were homozygotes at codon 117 (Ala/Ala, gca/gca) and 171 (Asn/Asn, aac/aac). There were no valine homozygotes (Val/Val) in our 419 subjects, and nine subjects (2.1%) showed methionine-valine heterozygosity (Mal/Val, atg/gtg). The methionine homozygotes (Met/Met) comprised the major population (97.9%), and the prevalence of distribution is different to that seen in Caucasians. The almost 100% conservation of the domain from codon 117 to 171 implies the warranty of PrP in cellular functions. The high prevalence of Met/Met alleles in Taiwan did not imply an increased risk of CJD, and the genetic susceptibility of CJD by codon 129 of PrP may be still elusive for the infectivity.