For the clinician who works in a behavioral-medicine or primary-care setting, this article presents the association between medical illness and suicide. Specific illnesses such as HIV/AIDS, cancers of the brain and nervous system, and multiple sclerosis all are associated with an increased risk of suicide. Rates of major depression rise with increasing rates of serious medical illness; however, depression and associated suicidal ideation tend to be undertreated in the medically ill. When medical illness becomes terminal, the clinician's patient may be confronted with difficult end-of-life decisions. Great concern exists in the United States about the ethics of end-of-life decision making and the issue of physician-assisted suicide. The latter part of this article examines the terminally ill patient's right to refuse life-sustaining treatments or to have death hastened according to the principle of the "double effect." It also reviews psychologists' apparent acceptance of the concept of rational suicide, as well as assisted suicide under certain conditions, and offers several caveats. A reexamination of psychology's role, standards, and principles with respect to rational suicide is recommended.