The　prevalent　CYP3A5　*3　and　the　functional　multi-drug　resistance　gene　(MDR1)　C3435T　show　marked　interethnic　variation　among　Orientals,　Caucasians　and　Africans.　This　study　aimed　to　investigate　the　distribution　of　CYP3A5*3　and　MDR1　C3435T　among　Chinese　ethnic　groups.　Genotypes　of　the　CYP3A5*3　and　MDR1　C3435T　were　determined　in　839　unrelated　healthy　Chinese　subjects　by　using　polymerase　chain　reaction-restriction　fragment　length　polymorphism　(PCR-RFLP)　assays.　Frequencies　(P　＜　0.05)　of　CYP3A5*3　variant　alleles　observed　in　Uygur　Chinese,　Kazakh　Chinese　and　Tibetan　Chinese　(88.1%,　84.5%　and　80.7%,　respectively)　were　Significantly　higher　than　those　in　Han　Chinese,　Wa　Chinese　and　Bai　Chinese　(67.3%,　56.3%　and　70.2%,　respectively).　Significantly　higher　3435T　variant　frequencies　(P　＜　0.05)　were　observed　in　Uygur　Chinese　(58.4%)　and　Kazakh　Chinese　(56.8%)　compared　with　Han　Chinese　(44.2%),　Tibetan　Chinese　(43.9%),　Wa　Chinese　(45.8%)　and　Bai　Chinese　(44.2%).　These　results　indicate　that　there　were　marked　ethnic　differences　in　the　mutant　frequencies　of　CYP3A5*3　and　MDR1　C3435T　among　Chinese　ethnic　groups.　Frequencies　of　those　variants　observed　in　Uygur　Chinese,　Kazakh　Chinese,　Tibetan　Chinese,　Wa　Chinese　and　Bai　Chinese　were　intermediate　between　those　seen　in　Han　Chinese　and　African-American.