We have confirmed the expression of CCK-A and CCK-B receptor mR NA in the lung tissues of SD rats by reverse transcribed polymerasechain reac tion (RT-PCR). The expression of CCK-A and CCK-B receptor mRNA in the lung was i dentified by means of second-amplification and southern blotting. The experiment showed the RT-PCR product of approximately 1.3kb from the CCK-A receptor mRNA a nd approximately 480bp from the CCK-B receptor mRNA. Our result provided the fun dament of molecular biological experiment for further studing out the mechanism of CCK-8 protecting lung from injury when endotoxin shock occurs.