AIM: To investigate the genotype and allelic frequencies of Cytochrome P450 2B6 polymorphisms in four south Chinese populations.METHODS: DNA was obtained from blood samples from Han Chinese from Hong Kong and three minority groups,the Wa, Bulang and Lahu from Yunnan in south China. Genotyping was performed using real-time PCR and confirmed by direct sequencing.RESULTS: A total of 507 subjects from south China were studied. Results showed there is a high prevalence of 516G ＞ T (34.5%) in ethnic Chinese compared to literature reports on other Asian populations and Caucasians. The frequency of the 516TT genotype is higher in the Hah majority (23.1%) than in three other ethnic minority groups (i.e., 7.4%, 9.1% and 15.8%) in south China.CONCLUSION: This was the first study to document the spectrum of CYP2B6 allelic variants and genotypes in a south Chinese population. The 516G ＞ T allele is associated with a defective metabolism of efavirenz (EFV), which therefore may predispose to drug toxicity.Treatment regimens for human immunodeficiency virus (HIV) and heroin addiction may need to be optimized in different populations because of the marked variability of the key metabolizing enzyme.