['Setting treatment goals in the intensive care unit (ICU) often involves resuscitation decisions. Our objective was to study the rate of establishing do-not-resuscitate (DNR) directives, determinants, and outcomes of those directives for mechanically ventilated patients.', 'In a multicentre observational study, we included consecutive adults with no DNR directives within 24 hr of ICU admission who were mechanically ventilated for at least 48 hr. We identified the rate with which DNR directives were established, and factors associated with these directives.', 'Among 765 patients, DNR directives were established for 231 (30.2%) patients; 143 (62.1%) of these were established within the first week. Factors independently associated with a DNR directive were: patient age [> or = 75 yr (hazard ratio [HR] 2.3, 95% confidence interval 1.5-3.4], 65 to 74 yr (HR 1.8, 1.2-2.7), 50 to 64 yr (HR 1.4, 1.0-2.2) relative to < 50 yr); medical rather than surgical diagnosis (HR 1.8, 1.3-2.5); multiple organ dysfunction score (HR 1.7 for each five-point increment, 1.4-2.0); physician prediction of ICU survival [< 10% (HR 15.0, 6.7-33.6)], 10 to 40% [(HR 5.0, 2.3-11.2), 41 to 60% (HR 4.0, 1.8-9.0) relative to > 90%]; and physician perception of patient preference to limit life support (no advanced life support [(HR 5.8, 3.6-9.4) or partial advanced life support (HR 3.2, 2.2-4.6) compared to full measures].'] Are dNR directives established early in mechanically ventilated intensive care unit patients?