Critically ill patients of intensive care units (ICUs) are at particular risk for developing nosocomial bloodstream infections. It is important to know the pathogens causing nosocomial bacteraemia in the ICUs and their antimicrobial sensitivity to formulate appropriate treatment guidelines. We conducted a study from July to December, 2001 in the ICUs of a tertiary care centre in northern India. The records of all the patients who had one or more episodes of nosocomial bacteraemia during the study period were reviewed to identify the pathogens causing bacteraemia and their antimicrobial sensitivities. The source of bacteraemia was ascertained on the basis of a concomitant positive culture from another body site with the same bacteria having a similar antimicrobial sensitivity pattern. A total of 152 episodes of nosocomial bacteraemia occurred in 140 patients. Of these, 148 (97%) episodes were monomicrobial, with Pseudomonas aeruginosa (21%) being the commonest isolate. Overall, Gram negative bacteria accounted for the majority (71%) of isolates. A source of bacteraemia was identified in 49 (32%) episodes, with lower respiratory tract being the commonest (49%) source. A high rate of antimicrobial resistance was observed amongst the isolates, all enterococci having high level aminoglycoside resistance and 89 per cent Gram negative bacteria producing extended spectrum beta-lactamases. A high prevalence of antimicrobial resistance in isolates causing bacteraemia in these critical care wards warrants implementation of strict antibiotic prescribing policies and hospital infection control guidelines.