The rapid spread of antibiotic resistance among gram negative bacteria (GNB) is an emerging threat and a matter of apprehension worldwide. Several mechanisms for the resistance of pathogenic organismshave been established, of which established one is the enzymatic hydrolysis of the antibiotic by specific enzymes called b -lactamases. The present study was undertaken to determine the prevalence of various b -lactamases in the multidrug resistance (MDR) gram negative bacilli from a tertiary care hospital. A totalof 596 consecutive, non- duplicate MDR GNB strains were isolated from various clinical samples which were received over a period of one year. The organisms were identified by standard biochemical tests and antibiotic susceptibility was determined by disc – diffusion method using Clinical Laboratory Standard Institute (CLSI) guidelines.  They were then screened for the b-lactamase production. statistical analysis was done by using Chi square test. A total of 596 MDR isolates, 503 (84.39%) were b- lactamase producers from which 306 (51.34%) were AmpC producers, followed by 118 (31.54%) ESBL producers and 115 (19.29%) were MBL producers. The ESBL production was maximally seen in Escherichia coli, while the AmpC production was mainly observed in Enterobacter spp. and major MBL producer was Acinetobacter spp. The co production of the ESBL/MBL/ AmpC b- lactamases was observed in 105 (20.87%) strains. The present study revealed the high prevalence of b-lactamases among the MDR gram negative isolates which advocates an urgency of an early detection of b-lactamase producing organisms and thus an indiscriminate use of the higher antibiotics could be restricted as far as possible.