Some people here seem to be discussing euthanasia as suicide. It isn't and shouldn't be discussed that way. We are not talking about taking your life because of being depressed over a diagnosis or feeling suicidal due to mental illness. We are talking euthanasia. Where a person is, most commonly, already dying, suffering, in agony, possibly having machines hooked up to them to help keep them alive, possibly in and out of consciousness, with maybe no means of coherent thought or communication anymore. At this point, granting that they have either made their wishes known by living will or by informing loved ones of their desire not to live in such a condition, if it is the moral thing to do to either disconnect them from supporting machines or perhaps turn up a morphine drip until they, painlessly, fall asleep and pass away.
In reference to various previous posts...it has nothing to do with cars, train tracks, sharp objects, or any of the like. That is suicide. Euthanasia is something performed by doctors/loved ones on behalf of the suffering person.