Abstract: Objective To study serotonin transporters (SERT) in postmortem human brains of Parkinson's disease (PD). Methods Immunoautoradiography was used to reveal SERT distribution in postmortem PD brains. Results In comparison with healthy group, SERT decreased in dorsal raphe nucleus, substantia nigra and striatum in PD brains. Quantitative analysis revealed that 25.9%、31.1%、27.2% and 24.7% of labeling intensity of SERT decreased in putamen, caudate nucleus, substantia nigra and ventrotegmental area as compared with corresponding control respectively. Among the four regions studied of dorsal raphe nucleus,SERT labeling intensity significantly decreased 38.9%, 37.3%, 16.5% and 37.0% of corresponding control respectively in ventral part，dorsal part，caudal part and interfascicular part. Median raphe nucleus did not show the decreased SERT labeling. Conclusions Decreased SERT expression in three regions of postmortem PD brains indicates that a dysfunction of serotonergic raphe system may contribute to the etiology of Parkinson's disease.