The doctor's dilemma regarding life support arises from opportunities in modern medicine to prolong life beyond the wildest dreams of medical doctors in previous eras. The traditional ethical framework based on duties to respect life, do what is best for the patient, be faithful to patients' reasonable expectations and avoid doing harm provides an adequate general guide for practitioners regarding what they are ethically required to do and must refrain from doing. However, a third category, ethical permissibility, allows for conduct that may not be ideal but is the most ethical in life-support dilemmas. Discussions of withholding and withdrawing life support, ordinary and extraordinary measures, proportionality and medical futility are enriching today's ethical debate about ethically permissible conduct in such situations.