To explore the effect of G72/G30 polymorphisms on the clinical manifestations of schizophrenia, especially on the age at onset and sex of patients, we examined three single nucleotide polymorphisms in 216 schizophrenic patients and 321 healthy controls. Significant associations of schizophrenia with the A allele of rs947267 (P=0.012) and haplotype A-A-G (rs2391191-rs947267-rs778294) (P=0.008) were found in early-onset schizophrenic patients. So did the same allele (P=0.034) and haplotype (P=0.009) as mentioned above in male patients. These findings suggest that the G72/G30 gene may modulate the age at onset and there might be a potential interaction between this locus and sex in the pathogenesis of schizophrenia.