Ordinarily, when discussing treatment options with a patient, doctors manage to fulfill an ethical obligation by ensuring that the patient's treatment choices are accommodated as far as possible. The four key ethical principles are: beneficence, non-maleficence, respect for autonomy, and justice. One of the cornerstones of good medical practice is that before providing treatment or involving a patient in teaching, or research, doctors must be satisfied that they have a valid authority. Usually this requires the patient to consent to the proposed treatment. In critical care the hardest decisions are those concerning when to withhold or withdraw treatment. Despite this the majority of patients who die in critical care departments do so after a decision to withhold or withdraw life-prolonging care. When considering end-of-life issues, good communication with patients and their relatives is essential for establishing priorities and ensuring that the wishes of the patient are paramount.