This study aimed to examine the incidence and characteristics of infections in intensive care unit (ICU) patients and to assess their outcomes. An international prospective cohort study was conducted in 28 ICUs across eight countries from May 1997 to May 1998. A total of 14,364 patients were admitted, with 6,011 staying less than 24 hours and 8,353 more than 24 hours. Overall, 3,034 infectious episodes were recorded at ICU admission (crude incidence: 21.1%), and 1,581 during the ICU stay. Respiratory, digestive, urinary tract, and primary bloodstream infections accounted for about 80% of all sites. Hospital-acquired and ICU-acquired infections were more frequently microbiologically documented than community-acquired infections. About 28% of infections were associated with sepsis, 24% with severe sepsis, and 30% with septic shock. Crude hospital mortality rates ranged from 16.9% in non-infected patients to 53.6% in patients with hospital-acquired infections at ICU admission and further developing ICU-acquired infections. The study highlights the high incidence of infections in ICUs and the significant impact of nosocomial infections on ICU resource utilization and patient outcomes.This study aimed to examine the incidence and characteristics of infections in intensive care unit (ICU) patients and to assess their outcomes. An international prospective cohort study was conducted in 28 ICUs across eight countries from May 1997 to May 1998. A total of 14,364 patients were admitted, with 6,011 staying less than 24 hours and 8,353 more than 24 hours. Overall, 3,034 infectious episodes were recorded at ICU admission (crude incidence: 21.1%), and 1,581 during the ICU stay. Respiratory, digestive, urinary tract, and primary bloodstream infections accounted for about 80% of all sites. Hospital-acquired and ICU-acquired infections were more frequently microbiologically documented than community-acquired infections. About 28% of infections were associated with sepsis, 24% with severe sepsis, and 30% with septic shock. Crude hospital mortality rates ranged from 16.9% in non-infected patients to 53.6% in patients with hospital-acquired infections at ICU admission and further developing ICU-acquired infections. The study highlights the high incidence of infections in ICUs and the significant impact of nosocomial infections on ICU resource utilization and patient outcomes.