A multidisciplinary research program on levels of care was conducted in 15 adult intensive care units in North America, Europe, and Australia. The program addressed advance directives for cardiopulmonary resuscitation, provision of advanced life support, and clinicians' discomfort with evolving treatment plans. The results indicated that the factors that determined the establishment of directives for advance life support differed from the factors that informed a decision to limit or withdraw support after admission to an intensive care unit. In addition, clinicians' prognoses were imprecise and often an underestimation of the probability of short-term survival. Finally, some degree of discomfort was common in care providers in the intensive care unit, most often because they thought interventions were excessive and not compatible with an acceptable future quality of life. The provision of advanced life support mandates explicit decision making about how life-support measures should be used.