Previous candidate gene studies of major depressive disorder (MDD) have provided inconclusive evidence of association for genes with strong biological rationale for MDD. In this study, we aimed to investigate the association of tryptophan hydroxylase 2 gene with MDD and its treatment response in the Chinese Han population.Three hundred and sixty eight depressed patients who met DSM-IV criteria for major depressive disorder were recruited for the study. 371 normal controls were recruited from local community. Patients and normal controls were genotyped for TPH2 (rs4290270 and rs7305115) variants by polymerase chain reaction. Male and female subjects were analyzed separately.No differences were found in the frequencies of the single alleles and genotypes of the tested polymorphisms between MDD patients and normal group. The frequency of the A-A haplotype was significantly higher in female MDD compared to healthy female controls (P<0.05). No significant association with treatment response was discovered in haplotype and single-marker analysis.This study lacks a placebo control and we cannot definitively exclude the possibility that some patients in the responder group responded to the placebo effect alone.The result suggests that TPH2 gene may have a gender dependent effect on susceptibility to MDD but not with its treatment response in Chinese Han population. Further studies are needed to replicate the association that we observed.