Abstract: Excessive consumption of antimicrobial materials in hospitals and the community is as the main encoder, led to the emergence, development and acquisition of new bacterial resistance to antimicrobials. According to the lack of the enough information about the mechanism of the resistant genes to disinfectants and receiving no report from the country about this study and with the aim of considering the resistance or sensitivity of the isolates of the Acinetobacter baumannii MDR in facing disinfectants, this study was taken place in the selected intensive care units if the hospitals of Tehran. This study which was conducted over a period of 10 months, Acinetobacter baumannii species were separated by culture and biochemical tests. The resistance and sensitivity of the isolates to antibiotics is considered according to CLSI guidelines. By multiplex PCR Method blaCTX and blaTEM were detected and finally, MDR strains were treated with 2% glutaraldehyde. In the study 131 isolates (22/28%) of Acinetobacter baumannii were isolated. The amount of the resistance to various antibiotics was in the range of the 69/4 to 100%. The percentage of frequency of the blaTEM and blaCTX was 3/2% and 19/4%, respectively. And there was seen no resistance to glutaraldehyde. It seems that beside variety and prevalence of blaTEM and blaCTX, enormous mechanisms like porin and leaking systems (efflux Pumps) are responsible in the making of the resistance of Acinetobacter baumannii to disinfectants. Also, these results facilitated the study of phenotypic and genotypic resistance patterns of these antimicrobials and disinfectants in different parts of the world.