Dr. Mark Siegler is a founding figure in the field of clinical medical ethics. His seminal publications asserted clinical medical ethics as a worthwhile field and demonstrated its necessity within the practice of medicine. Dr. Siegler further encouraged the development of this field through the foundation of a fellowship training program in which hundreds of physician and other medical workers have learned the principles of clinical medical ethics. Through the efforts of Dr. Siegler and his many fellows, the field of clinical medical ethics is now taught, studied, and practiced internationally. By expanding the field as such, Dr. Siegler can be credited with improving the quality of health care for patients across the modern world.