Background: The rapid emergence of antibiotic Resistance, especially broad-spectrum antibiotics, resulted in the avid use of new potent antibiotics. Ceftriaxone and ceftazidime, two third-generation cephalosporin, are usually used to manage complicated and uncomplicated infections. The use of cefepime in resistant infections is increasing gradually, which put this potent antibiotic at risk of Resistance.Patients and methods: During an 18-month period, a total of 220 gram-Negative bacteria including Pseudomonas spp, Serratia spp, Acinetobacter spp, Proteus spp, E-coli and Klebsiella spp. have been isolated by standard microbiological methods from nosocomial surgical site, abscess, blood stream and urinary tract infections. MIC of antibiotics on isolated bacteria was determined by gradient concentration method.Results: Totally, 29.4%, 19.5% and 23.3% of isolated bacteria with MIC£8μg/ml were sensitive to cefepime, ceftriaxone and ceftazidime, respectively. High level Resistance with MIC³256mg/ml to cefepime, ceftriaxone and ceftazidime was also observed in 47.1%, 70.8% and 62.5% of cases, respectively (p<0.05). High level Resistance to cefepime were more commonly observed for pseudomonas (73.1%) and Klebsiella spp. (73.5%), respectively (p<0.05). Conclusion: According to CLSI criteria, 47.1% of isolated bacteria in this study showed high level of Resistance (MIC³256mg/ml) to cefepime. Therefore application of cefepime, as a drug of choice, for gram-Negative organisms is not reasonable. Our result demonstrated that this potent antibiotic should not be used as a choice for empiric antibiotic therapy, in the cases of nosocomial infections caused by gram-Negative organisms.