In daily routine work clinicians of all specialties must make a variety of decisions, including whose needs and problems to address first, what diagnostic tests to order, what treatments to recommend or institute, how to measure the results of those treatments interventions, how to predict the fate of the patients, and when to stop the diagnostic or therapeutic process. Those challenges and questions are particularly concentrated in the setting of an intensive care unit where the time to make decisions is limited by the acute nature of the underlying diseases, where available information is commonly incomplete, and where the consequences of decisions are frequently of immediate and major importance to the patients. Resuscitating, providing life support, and providing intensive monitoring in a setting of advanced diagnostic and therapeutic technology requires clinicians to rapidly decide who should receive such care, what are the potential alternative management strategies, and what are the risks, benefits and costs of each alternative. In making a final management decision clinicians must also consider patients and relatives’ values and preferences, as well as the societal, cultural, religious, moral, and legal implications of their choices.