In recent decades medicine has gained dramatic new abilities to prolong life. Patients with kidney failure can be placed on renal dialysis; patients who have suffered cardiac arrest can sometimes be revived with advanced life-support measures including drugs, electric shock, airway intubation and closed or open heart massage; patients with pulmonary disease can be assisted by mechanical ventilation on respirators; and patients unable to eat or drink can receive nourishment and fluids intravenously or with tube feedings. These are only some of the most dramatic and well-known additions to medicine's armamentarium for staving off death in the gravely ill. While these and other life-sustaining treatments often provide very great benefits to individual patients by restoring or prolonging functioning lives, they also have the capacity to prolong patients' lives beyond the point at which they desire continued life support or are reasonably thought to be benefitted by it. Thus, where once nature took its course and pneumonia was the “old man's friend,” now increasingly someone must decide how long a life will be prolonged and when death will come. This chapter addresses some of the principal moral issues and arguments in current debates about life support. First, I address very briefly a related issue: the definition of death.