Background. Principle-based ethical theory is currently available to guide health care professionals in clinical decision-making when they face ethical dilemmas. These principles include respect for autonomy (RA), nonmaleficence (NM), beneficence (B), and distributive justice. It is, however, unknown which principles, if any, guide physicians and nurses in this decision-making. The goal of our study was to explore how anesthesiologists, surgeons, nurses, and nurse anesthetists reason in the face of a moral dilemma. Methods. By an anonymous survey we asked: Would you give a blood transfusion to a young, ASA I, Jehovah's Witness who clearly refused transfusion, in a case of a life-threatening bleeding? What ethical principle did you apply in your decision? We presented this question before and after a 1-hour ethical tutorial about these principles. Results. Twenty-nine anesthesiologists, 41 surgeons, 21 surgical nurses, and 33 nurse anesthetists participated in our survey. We found that 59%, 30%, 29%, and 36% of anesthesiologists, surgeons, surgical nurses, and nurse anesthetists, respectively, would give a blood transfusion despite the patient's demand. Nurses used B, surgeons NM, and anesthesiologists B and NM to justify trans-fusion. However, two among 11 anesthesiologists and five among 12 surgeons did not explain their choice. Those who tend to withhold blood transfusion overwhelmingly used RA as the principle behind this decision. Nine participants changed their view before and after the tutorial. There was no correlation between gender, age, and professional experience with the choice of principle. The average interest score for the tutorial was 74/100 for all participants after this ethical course. Conclusions. Anesthesiologists tend to transfuse Jehovah's Witness patients more than did the others. Together with surgeons, they explicitly justify their decision-making less frequently when compared with nurses and nurse anesthetists. Further education in ethical theory is appreciated and needed.