To determine the incidence, risk factors for, and the influence of bloodstream infections (BSIs) on mortality of patients in intensive-care units (ICUs), prospectively collected data from all patients with a stay in an ICU >48 h, during a 1-year period, were analysed. Of 572 patients, 148 developed a total of 232 BSI episodes (incidence 16·3 episodes/1000 patient-days). Gram-negative organisms with high level of resistance to antibiotics were the most frequently isolated pathogens (157 strains, 67·8%). The severity of illness on admission, as estimated by APACHE II score (OR 1·07, 95% CI 1·04–1·1, P<0·001), the presence of acute respiratory distress syndrome (OR 3·57, 95% CI 1·92–6·64, P<0·001), and a history of diabetes mellitus (OR 2·37, 95% CI 1·36–4·11, P=0·002) were risk factors for the occurrence of BSI whereas the development of an ICU-acquired BSI was an independent risk factor for death (OR 1·76, 95% CI 1·11–2·78, P=0·015). Finally, the severity of organ dysfunction on the day of the first BSI episode, as estimated by SOFA score, and the level of serum albumin, independently affected the outcome (OR 1·44, 95% CI 1·22–1·7, P<0·001 and OR 0·47, 95% CI 0·23–0·97, P=0·04 respectively).