In an effort to develop the tools for monitoring the contamination of xenoestrogen in the aquatic environment of Korea, reverse transcription-polymerase chain reaction (RT-PCR) analysis of vitellogenin (VTG) mRNA expression were optimized in Synechogobius hastus. Based on the partial VTG cDNA sequence VTG mRNA level in livers from male fishes was analyzed by RT-PCR. As an internal control beta actin mRNA was amplified. 3 ${mu}g$ of total RNA was reverse transcribed in 20 $mu$l reaction using murine leukemia virus 〔MuLV〕 reverse transcriptase. Subsequent PCR using the 1 ${mu}g$ of cDNA resulted in linear increase in PCR product of VTG in female liver cDNA from 10 to 30 cycles of amplification. On the contrary, in male, PCR product first detected at 28 cycles of amplification and linearly increased during 38 cycles of amplification, suggesting that male S. hastus expresses minute amount of VTG mRNA which is $2^{-18}$ equivalent of female. In conclusion, the optimized protocol of VTG mRNA expression in the liver of male S. hastus will be promising the environmental monitoring the xenoestrogen contamination in the western coast and estuaries in Korea.