ObjectiveTo study the drug resistance of extendedspectrum betalactamasesproducing and plasmidmediated AmpC betalactamasesproducing Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) in a hospital. MethodsOne hundred and thirtynine strains of  E. coli and 102 strains of K. pneumoniae were collected from clinical specimens form November, 2006 to July,2007. ESBLs production was detected by the standard disk diffusion method, and AmpC production was detected by cefoxitin threedimensional test of enzymeextraction. Drug susceptibility was detected by KirbyBauer disk diffusion method, the result were analysed by American NCCLS Standard.ResultsAmong 139 strains of E.coli, ESBLsproducing, AmpC betalactamaseproducing, both ESBLs and AmpC betalactamaseproducing E.coli was 48.20%, 9.35% and 2.88% respectively; among 102 strains of K.pneumoniae, the isolation rate was 55.88%, 8.82% and 2.94% respectively. The resistant rate of ESBLsproducing strains to caphalosporins, aminoglycosides and monobactams was obviously higher than those of nonESBLsproducing strains (P<0.001~0.05), except carbapenem and ceftazime, plasmidmediated AmpC betalactamaseproducing strains revealed a high drug resistance to the second and third generation cephalosporins and quinolones (P<0.001~0.05). ConclusionProduction of ESBLs and AmpC  in bacteria are important factors in  drug resistance. More attention should be paid to the use of antimicrobial agents and control of nosocomial infection.