Objective To inve stigate the status of the drugre sistance and the ampC gene expre ssion of Enterobacter cloacae1 Methods Disk diffusion test swere made for detecting the susceptibility of antimicrobial agents against Enterobacter cloacae1 AmpC gene was amplified by polymera se chain reaction (PCR) and verified by DNA sequencing1 AmpC gene expression was analyzed according to antimicrobial agent sensitive phenotype. Results The sensitivity rates of 144 strains to imipenam, cefepime and cefoperazone/sulbactam were 98161%, 65197% and 63189%, respectively. The sensitivity rates of 144 strains to other antimicrobial agent swere lower. Among the 144 strains 120 were found to be po sitive by PCR for ampC. The PCR product showed high homology to the GenBank ampC sequence1 Stably derepre ssed strains, hyperinducible strains and unexpre ssing or lower level expre ssing strains accounted for 3010% (36/120), 3715% (45/120), and 3215% (39/120), re spectively1 Fifty-six out of 120 strains (46167%) also produced extended spectrumβ-lactama se s (ESBLs). The hyperinducible strains were highly sensitive to all the antimicrobial agents except amoxicillin/ clavulanic acid and cefuroxime, while the stably derepre ssed strains were only sensitive to imipenam and cefepime1 However, sensitivity to cefepime decrea sed if the strains also produced ESBLs. Co nclusions The durg re sistant status of Enterobacter cloacae is severe1 Clearing out the expre ssive status of ampC gene will be helpful in selection of antimicrobial agents in the treatment of clinical infection.