The objective of this study was to determine the incidence of episodes of transmission of nosocomial pathogens and of those pathogens leading to nosocomial infections. Over a period of 18 months all patients from 5 intensive care units (ICUs) who stayed for more than 2 days were included in this study. Surveillance of nosocomial infections was carried out and all isolates of 10 of the most frequent pathogens in ICUs (indicator pathogens) were collected and typed. A total of 28,498 patient days and 431 nosocomial infections were observed (incidence density 15.1 per 1,000 patient days), among them 278 caused by 1 of the selected indicator pathogens. A total of 141 episodes of transmissions were identified, corresponding to an incidence of episodes of transmission of 5.0 per 1,000 patient days and 41 nosocomial infections were transmission-associated, corresponding to 14.5% of all nosocomial infections. The data of this study demonstrate that even in ICUs with average nosocomial infection rates, some nosocomial infections could be avoided.