This paper examines the controversial and complex issues of euthanasia and physician-assisted suicide (PAS). I begin by defining and distinguishing these two terms and explain how they relate to each other. I also describe the medical doctrine of double effect, in which relieving pain comes at the expense of hastening death. Then, I give a brief overview of the common law defense of necessity, which is practically the sole defense available to or used by physicians accused of committing euthanasia or PAS. Finally, I analyze the legal doctrines of euthanasia and PAS, focusing on legislation and cases in the European Union — primarily the United Kingdom, the Netherlands, and Switzerland — and the U.S. states of Oregon, Washington, and Montana.