Objectives : Schizophrenia is equally distributed in both sexes. However, later-onset, milder psychopathology, and better outcome are associated with the females. This reason is thought to be partly due to the estrogen system. Recently, it was suggested that estrogen receptor 1(ESR1) gene polymorphisms might affect the expression of ESR1 and were associated with several psychiatric disorders. Thus, we investigated the association between two single nucleotide polymorphisms(SNPs) in the ESR1 gene and Korean schizophrenic patients in this study. Methods : Genotype, allele, and haplotype frequencies of the two SNPs(rs 2234693 and rs 2228480) were analyzed between 218 Korean controls and 158 Korean schizophrenic patients. Also, age of onset and negative symptom scale scores according to genotypes were analyzed in the patients with schizophrenia. Results : There was a significant difference in allele frequencies of rs 2234693 between the schizophrenic patients and the controls(p=0.03). Genotype distributions(p=0.03) and allele frequencies(p=0.01) of rs 2234693 were significantly different between the female schizophrenic patients and the female controls. The frequency of TC-CC genotypes compared with TT genotype in the female schizophrenic patients was significantly higher than that in the female controls(OR=2.36). The mean age of onset in the schizophrenic patients with TC-CC genotypes was significantly lower than that in the patients with TT genotype. The frequency of rs 2234693C- rs 2228480G haplotype in the female schizophrenic patients was relatively higher than that in the female controls. Conclusions : These results of our study support the possibility that the ESR1 gene polymorphisms might be involved in the susceptibility of females to schizophrenia and play a role in sex difference of schizophrenia.