Pseudomonas aeruginosa and Acinetobacter baumannii which are usually multiply antibiotic resistant, are the most important agents causing infections in intensive care units (ICUs). The aim of this study was to determine the antibiotic sensitivity patterns of P. aeruginosa and A.baumannii that cause infections in ICUs and hospital service units and to follow the variation in resistance between the years of 2003 to 2006. P. aeruginosa (n:1071) and A.baumannii (n:587) strains were isolated from blood, urine, wound, sterile body fluid, sputum and tracheal aspirate cultures of patients who were diagnosed to have infections in ICUs and hospital service units. Conventional methods were used for the identification of the bacteria, and antibiotic sensitivies of the isolates were investigated by disk diffusion method. The most effective antibiotics in 2003 were piperacillin-tazobactam (84%), ciprofloxacin (79%), imipenem (77.5%), and meropenem (69%) for P. aeruginosa strains isolated from ICUs. Decreasing sensitivities to imipenem (51%), meropenem (45%), cefepime (51%), piperacillin (38.5%), ciprofloxacin (72%), cefoperazone/sulbactam (44%) and piperacillin/tazobactam (67%) for P. aeruginosa were found statistically significant in 2006 (p < 0.05). The most effective antibiotics were meropenem (98%) imipenem (94%) and ampicillin/sulbactam (72%) for A.baumannii strains isolated from ICUs in 2003. Decreasing sensitivities to imipenem (60.5%), meropenem (69%), cefepime (24%), ciprofloxacin (14%), gentamicin (13%), and amikacin (19%) for A.baumannii were statistically significant in 2006 (p < 0.05). Our data have indicated that P. aeruginosa and A.baumannii strains isolated in ICUs at our hospital showed multi-drug resistance in 2006, with significant increases since 2003 against certain antimicrobial agents. In conclusion there is an urgent need for effective strategies to control the use of antibiotics in our hospital.