Throughout history, men have repeatedly made judgments regarding their own conduct and that of their fellow men. Some acts have been judged to be right or good, while other acts have been denounced as wrong or evil. Ethical judgment in medicine, as in other areas of life, is an attempt to distinguish between good and bad conduct. This book is based on three lectures given by the author as the Medical Director of Eye Clinic Singapura International. The first lecture was an address delivered to medical undergraduates at the National University of Singapore in 1975. The second was a Commonwealth Medical Association lecture delivered a decade ago. The third was a Singapore Medical Association lecture delivered in 1981. This volume, emphasizing the principles of medical ethics, has been kept simple and brief, and it is hoped that it will make interesting reading for both medical professionals and the general public.