Context: Professionalism remains a challenging part of the medical curriculum to define, teach and evaluate. We suggest that one way to meet these challenges is to clarify the definition of professionalism and distinguish this from medical ethics. Methods: Our analysis is two staged. First, we reviewed influential definitions of professionalism and separated elements relating to (a) ethico-legal competencies, (b) clinical competence and (c) professionalism. In reference to professionalism, we then distinguished between aspirational virtues/values and specific behaviours. From these, we develop a working definition of medical professional behaviour consisting of six domains of behaviour: responsibility; relationships with and respect for patients; probity and honesty; self awareness and capacity for reflection; collaboration and team work; and care of colleagues. Second, we tested this working definition against empirical data concerning disciplinary action against practising doctors using (a) sources in the literature and (b) an original analysis of complaints received by the Medical Board of South Australia. Conclusion: Our empirical analysis supports the relevance of four of the six potential domains: responsibility; relationships with and respect for patients; probity and honesty; self awareness and capacity for reflection. There are additional reasons for retaining 'collaboration and team work' in the medical professional behaviour curriculum but 'care of colleagues' may be better addressed in the ethico-legal curriculum. Our definition of professional behaviour is consistent with the theoretical literature, captures behaviours that predict future complaints against practitioners and is consistent with current complaints about professionalism in South Australian practitioners. This definition can further the teaching and assessing of professional behaviour in medical schools.