The purpose of this study was to determine the causative agents of nosocomial infections in intensive care unit and antibiotic resistance patterns of the agents. The study was a retrospective evaluation of the frequency of isolation and antimicrobial resistance patterns of 469 microorganisms isolated from 820 clinical specimens obtained from 84 patients with suspected infection hospitalized in the Anesthesia Intensive Care Unit, Osmangazi University Hospital, between January 1 and December 31, 2003. When considering all specimens, the culture positivity rate was 44.9%. A total of 368 samples was culture positive. In 75.6% of them only one microorganism was present, while in 24.4% two or more microorganisms were isolated. The most frequently isolated microorganisms were Acinetobacter spp. (28.4%), Staphylococcus aureus (19.8%) and Candida spp. (13.4%). The strains of Acinetobacter showed resistance to imipenem (59.7%), ciprofloxacin (78.4%), cefepime (79.2%), amikacin (83.9%), ceftazidime (90.1%) and cefotaxime (94.2%). The rates of methicilline resistance were 81.7% and 88.4% in S. aureus and coagulase-negative staphylococci isolates, respectively. All of the staphylococcal isolates examined were susceptible to vancomycin and teicoplanin. Candida albicans was the most frequently isolated Candida species (84.1%). Of Candida isolates 7.4% and 17.4% were resistant to fluconazole and itraconazole, respectively. Amphotericin B had an MIC50/90 of 0.064/0.19 µg/ml for Candida isolates.