In the present study, we reported distribution of ER alpha and ER beta mRNAs in the hypothalamus of young and old ovariectomized (OVX) rhesus macaques. The ER alpha were detected in all six major vestiblular nuclei which included arcuate nucleus (ARC) , paraventricularis nucleus (PVN) , periventricular nucleus (PeriV) , supraoptic nucleus (SON) , medial prioptic nucleus (MPN) and lateral hypothalamus area (LHA). However, the ER beta mRNA can also detected in those nuclei excerpt SON, but the signals of ER beta mRNA were weaker than those of ER alpha mRNA. We observed that the degree of expression of ERs mRNA were different in most nucleus of old and young monkeys. The ER alpha mRNAs were highly expressed in ARC and SON in young monkeys compared with old monkeys. Moderate amount of ERalpha mRNAs hybridization signals and weak signals were observed in LHA, and MPN both in young and old monkeys. In contrast, only lower level of ER alpha hybridization signal were observed in PVN and PeriV in young monkeys, and the signals of ER alpha were very low in those nucleus of old monkeys. In general, the expression of ER beta mRNA were weaker than that of ER alpha mRNA in above nucleus excerpt LHA. The relatively higher density of ER beta hybridization signals have been observed in the LHA in young monkey compared with old monkeys. Low amount of ER beta mRNA hybridization signals were observed in the ARC, PVN and MPN, and no age differences were seen in PVN and MPN of those monkeys. In PeriV, we observed some signals in young monkey and a few signals in old monkeys. It was different from the rodent in which we did not found ER beta hybridization signal in SON. This study showed that both of the two estrogen receptors not only had the same pattern of expression but also had many different patterns of expression. The different expression of ER alpha and ER beta mRNAs in the young and old monkey brain may imply diverse functions in different regions of the monkey brain.