American doctors, long accustomed to preserving lives, are coming under increasing pressure to help patients end their lives. Sometimes the demand is for “assisted suicide,” in which the physician supplies a hopelessly ill patient with the means to commit suicide. There also are calls for “active euthanasia,” when the physician ends the person's life. Proponents of “aid in dying” say a person who is suffering from a painful or terminal illness has the right to medical help in cutting life short. Opponents say the practice poses ethical problems. They say that legalizing voluntary euthanasia and assisted suicide could, among other things, lead to policies that sanction involuntary killing of the aged and infirm.