Gram-negative bacteria were found to be the predominant isolates in ICUs, causing 73% of nosocomial infections (Cormican, et al; 1996). They account for about 78.8% of cases of pneumonia, 70.2% of cases of UTIs and 65% of cases of sepsis (Barsic, et al ; 1997). The four most common GNB include E.coli, Ps.spp., Kb spp. and Enterobacter species accounting for 32 % of all Gram negative infections in ICUs (Barnard, et al; 2003). In recent years, there has been an increased incidence and prevalence of extended spectrum beta lactamases(ESBL); enzymes that hydrolyse and cause resistance to oxyimino-cephalosporins and aztreonam; production of beta lactamases are the leading cause of resistance to beta lactam antibiotics among Gram negative bacteria.Over that past 60 years, the use of successive generations of B- lactam antibiotics leads to generations of B-lactamases enzymes each more potent than the last (Martinez, et al; 2006), In our study IPM, AMC, CD, SAM were still the most potent against Gram negative bacilli isolated in CCU with decline of activity of other antibiotic specially aminoglycosides as (AK, CN, TOB) and cephalosporins CAZ