Fifty-seven patients developed an episode of catheter-related infection (CRI) in the bloodstream during their stay in the intensive care unit (cases) and were prospectively observed to establish the attributable mortality, increase in length of stay, and excess costs. Costs were estimated by multiplying the number of excess days of stay by the reimbursement provided. The outcomes for these cases were compared with those for matched control subjects without CRI. Eight cases were excluded as no control was found. Of the 49 cases, 31 were coagulase-negative staphylococci (CNS). The level of severity was similar for both groups (APACHE II 15.5 +/- 7. 2 versus 15.2 +/- 7.3). There were no significant differences (p > 0. 20) in the mortality observed in the hospital for the cases (22.4%, 95% confidence interval [CI] 0.3% to 34.9%) and the control subjects (34.7%, 95% CI 21.2% to 40.1%). Among the survivors, the hospital stay was increased by 19.6 d (95% CI -1.1; 40.4). This represents an added cost of 3,124 Euros per episode of CRI among the survivors. In conclusion, our cohort study failed to show a difference in attributable mortality due to CRI in intensive care unit patients. Nevertheless, these infections lead to an increase in hospital stay of approximately 20 d. Each episode of CRI represents an additional cost of more than 3,000 Euros.