From Azospirillum brasilense Yu62, we cloned and sequenced the upstream region of draTG. No identified genes were found in this region except for portion of nifH, which is transcribed divergently from draTG. However, some potential regulatory elements were found, which include downstream promoter elements (DPE), upstream activator sequences (UAS), and A + T-rich regions. This suggests that the region between draT and nifH might be a regulatory region rather than an encoding region, and the promoter of dra operon would probably be a RpoN-dependent promoter. A draT::cam transcriptional fusion plasmid pAT1 was constructed in pAF300. The expression of draT was studied in Escherichia coli and A. brasilense by Cmr assay. The result showed that draT could be transcribed in A. brasilense but not in E. coli while grown aerobically on an LD plate. This suggests that the transcription of draT needs some factors which are absent in E. coli, and the draT upstream region has the promoter function. Using the promoter-probe vector pCB182, a draT::lacZ transcriptional fusion plasmid pCT1 was constructed. beta-galactosidase activity was determined in vivo in E. coli, in the presence or absence of NifA of Klebsiella pneumoniae, respectively. The results demonstrated that NifA was not involved in the transcriptional regulation of draTG.