Results of 6-year body-site monitoring in an intensive care unit (ICU) are presented and antimicrobial resistance of gram-negative isolates analyzed. The study included 622 patients. Six hundred thirty-five bacterial isolates-causes of nosocomial sepsis, pneumonia, and urinary tract infections (UTIs)-were tested during the study. Gram-negative bacteria were the predominant isolates, causing 65% of cases of sepsis, 78.7% of pneumonias, and 70.2% of UTIs. Gram-negative isolates (454) were highly resistant to antimicrobials commonly used in the ICU, with the exception of imipenem. Resistance was 1.1% among pathogens responsible for UTIs, 6.7% among those causing sepsis, and 13.6% among those responsible for pneumonia. Klebsiella pneumoniae associated with pneumonia and sepsis was significantly less resistant to ciprofloxacin than were isolates from urine (22.8% and 13.9%, respectively, vs 44.4%). Pseudomonas aeruginosa strains responsible for pneumonia were less resistant to ceftazidime than were isolates causing sepsis and UTI (35.7% vs 51.3% and 51.5%, respectively). Acinetobacter calcoaceticus strains associated with UTI were significantly more resistant to netilmicin than were strains responsible for sepsis and pneumonia (83.3% vs 40.3% and 42.6%, respectively). The study confirmed that in addition to focused microbiologic surveillance, multiple-body-site monitoring can provide unique information about the sensitivity of the pathogens involved. The results suggest that antimicrobial resistance among nosocomial pathogens depends on the site of infection or the type of microbiologic specimen.