This article asks if there are morally compelling differences among allowing a patient to die by foregoing treatment, physician-assisted suicide, & active euthanasia. It discusses 8 cases & concludes that if we seek an ethical distinction between physician-assisted suicide & foregoing life-sustaining treatment, we will not find it in an analysis of intent or causation. The article also attempts to develop a key concept in the rediscovery of casuistry as a methodology in medical ethics.(10 Refs.)