This study is to compare the influence of CYP2D6 *3 and *4 genotypes and phenotypes on the metabolic activity of CYP2D6 in Chinese Han, Uygur and Kazakh ethnic groups.  Allele specific amplification (ASA) was used to determine the CYP2D6*3 and CYP2D6*4 genotypes.  Phenotypes of CYP2D6 in all subjects were determined using dextromethorphan as probe drug by HPLC methods.  Among the 132 Han subjects, one subject (0.76%) exhibited the *1/*3 combination, and one (0.76%) exhibited the *1/*4.  Among the 136 Uygur subjects, 4 subjects (2.94%) showed the *1/*3 combination, 12 (8.82%) showed *1/*4, 4 (2.94%) showed *4/*4, and one (0.74%) showed *3/*4.  Among the 116 Kazakh subjects, 2 (1.72%) exhibited the *1/*3 combination, 7 (6.03%) exhibited *1/*4, and one (0.86%) showed *4/*4.  This research revealed significant differences in the  occurrence frequencies of the CYP2D6 genotype between Han and Uygur ethnic groups, as well as between  Uygur and Kazakh populations.  However, no difference was found between Han and Kazakh populations.  In addition, the prevalence of PMs of the Uygur is comparable to that of the Caucasians.  However, the molecular mechanism underlying the poor metabolism is different in these two populations.