OBJECTIVE: To evaluate physicians' reasoning, considerations and possible difficulties in end-of-life decision-making for patients in European intensive care units (ICUs). DESIGN: A prospective observational study. SETTING: Thirty-seven ICUs in 17 European countries. PATIENTS AND PARTICIPANTS: A total of 3,086 patients for whom an end-of-life decision was taken between January 1999 and June 2000. The dataset excludes patients who died after attempts at cardiopulmonary resuscitation and brain-dead patients. MEASUREMENTS AND RESULTS: Physicians indicated which of a pre-determined set of reasons for, considerations in, and difficulties with end-of-life decision-making was germane in each case as it arose. Overall, 2,134 (69%) of the decisions were documented in the medical record, with inter-regional differences in documentation practice. Primary reasons given by physicians for the decision mostly concerned the patient's medical condition (79%), especially unresponsive to therapy (46%), while chronic disease (12%), quality of life (4%), age (2%) and patient or family request (2%) were infrequent. Good medical practice (66%) and best interests (29%) were the commonest primary considerations reported, while resource allocation issues such as cost effectiveness (1%) and need for an ICU bed (0%) were uncommon. Living wills were considered in only 1% of cases. Physicians in central Europe reported no significant difficulty in 81% of cases, while in northern and southern regions there was no difficulty in 92-93% of cases. CONCLUSIONS: European ICU physicians do not experience difficulties with end-of-life decisions in most cases. Allocation of limited resources is a minor consideration and autonomous choices by patient or family remain unusual. Inter-regional differences were found.