Electroantennogram (EAGs) were recorded from various aged and unmated males/females of oriental fruit flies (Bactrocera dorsalis Hendel) in response to methyl eugenol. The male flies of 14~24-day after emergence responded dramatically to the chemicals producing higher amplitudes in EAGs than those responses of other ages. In female flies, the amplitudes of EAGs were lower than males. We discussed the relationships of development of testes and ovaries.