In order to investigate the estrogen and estrogen receptor β changes after mating behavior of male mandarin vole ( Microtus mandarinus
), the radioimmunoassay (RIA) and immunohistochemistry methods were used to investigate changes of the serum estrogen (E) concentrations, estrogen immunoreactive neurons (E-IRs) and estrogen receptor β immunoreactive neurons (ERβ-IRs) in the relevant brain regions following mating behavior. Fifteen sexually matured male voles were randomly divided into three groups and treated differently: (1) control group: voles were exposed to clean hard-wood shavings (n
=5), (2) exposure group: voles were exposed to the soiled bedding for more than 24 h on which estrous females had been placed (n
=5), and (3) mating group: voles were placed with an estrous female for more than 24 h (n
=5). The results showed circulating serum E concentrations were significantly higher in the mating group than in the exposure group and the control group, and there were no significant difference between the exposure group and the control group. E-IRs and ERβ-IRs were detected in the following brain regions related to mating behavior: the arcuate nucleus (ARC), bed nucleus of the stria terminalis (BST), lateral septal nucleus (LS), medial amygdaloid nucleus (ME), medial preoptic area (MPO) and ventromedial hypothalamic nucleus (VMH). The results showed that there were significantly more E-IRs in the six brain regions in the mating group than in the control group and the exposure group, and there were no significant difference between the exposure group and the control group except for LS. There was no significant difference in ERβ-IRs in the six brain regions among the three groups, and there were some lighter -stained ERβ-IRs in these brain regions. The results suggested that estrogen affect mating activity of male mandarin voles, but ERβ might not play an important role in mating behavior of male mandarin voles. Instead, it might be through other receptors.