 1 risk ratio of susceptible homozygous genotypes set at 3, 2 risk ratio of heterozygous genotypes set at 1.5, 3 prevalence of phenotypes of interest set at 10. When SNPs with allele frequency of 0.15 are used in such conditions, approximately 135 cases and 270 controls are needed to reach this desired power. Expectedly, to obtain 135 subjects with atypical antipsychotics-induced diabetes, we need to examine about 1350 new schizophrenic patients treated with antipsychotics. Such an expectation implies that the pharmacogenetic study of atypical antipsychotics-induced diabetes is not feasible, however, in reality, the prevalence of hyperglycemia one of the components of X-syndrome among patients treated with antipsychotics may be higher than 10 in a Han Chinese population. In addition, the susceptible genotype may have a higher risk ratio. Thus, posterior power estimations may give even higher power than the conservative estimation even at a smaller sample size. Moreover, our samples will merge from samples from other medical centers. Thus, the task to examine 1350 schizophrenic patients treated with antipsychotics, is feasible. 