Thiaredoxin is a multifunctional protein that is ubiquitous in microorganisms, animals and plants. Previously, the expression of the Escherichia coli thioredoxin gene (tixA) was found to be negatively regulated by cAMP In the present study, the effect of temperature on the expression of the E. coli trxA gene was investigated. In order to examine the temperature effect, the fusion plasmid pCL70 that harbors the E. coli trxA P1P2 promoter was used. The other two fusion plasmids, pJH3 and pMG521 that were constructed in different vectors which harbor the E. coli trrA P2 promoter, were also used. When the E. coli strain MC1061/pCL70 was grown in a rich medium at 25℃, 34℃ and 42℃, the cells grown at 42℃ gave the highest β-galactosidase activity. The E. coli MC1061/pJH3 cells also revealed similar results. The E. coli MC1061/pJH3 and MC1061/pMG521 cells showed increased β-galactosidase activity utter the shift of the culture temperature to 42℃. The wild-type trxA gene of the E. coli MC1061 cells produced much higher thioredoxin activity at the higher temperature. These results support the conclusion that the E. coli trxA gene is regulated in a temperature-dependent manner. Especially the expression from its P2 promoter appeared to be sensitive to temperature.