Background: The four principles of Beauchamp and Childress - autonomy, non-maleficence, beneficence and justice - havebeen extremely influential in the field of medical ethics, and are fundamental for understanding the currentapproach to ethical assessment in health care. This study tests whether these principles can be quantitativelymeasured on an individual level, and then subsequently if they are used in the decision making process whenindividuals are faced with ethical dilemmas. Methods: The Analytic Hierarchy Process was used as a tool for the measurement (...) of the principles. Four scenarios, whichinvolved conflicts between the medical ethical principles, were presented to participants and they madejudgments about the ethicality of the action in the scenario, and their intentions to act in the same manner if theywere in the situation. Results: Individual preferences for these medical ethical principles can be measured using the Analytic HierarchyProcess. This technique provides a useful tool in which to highlight individual medical ethical values. Onaverage individuals have a significant preference for non-maleficence over the other principles, however, andperhaps counter-intuitively, this preference does not seem to relate to applied ethical judgements in specificethical dilemmas. Conclusions: People state they value these medical ethical principles but they do not actually seem to use them directly in thedecision making process. The reasons for this are explained through the lack of a behavioural model to accountfor the relevant situational factors not captured by the principles. The limitations of the principles in predictingethical decision making are discussed. (shrink)