Clinical professionalism is a set of values, behaviours and relationships which underpins the public's trust in healthcare providers both as individuals and organisations.  'First, do no harm' is expressed most clearly today in the patient safety movement and the imperative for transparency and candour in the delivery of healthcare.  Professional conduct is essential for safe and high quality clinical care. The ABC of Clinical Professionalism considers recent evidence on how healthcare practitioners maintain professionalism including how values are developed and affected by the working environment, the challenges of maintaining personal and organisational resilience and the ethical and regulatory framework in which practice is conducted.  Topics covered include: • Acquiring and developing professional values • Patient-centred care • Burnout and resilience • Confidentiality and social media • The culture of healthcare • Ensuring patient safety • Leadership and collaboration • Ethical and legal aspects of professionalism • Teaching and assessing professionalism • Regulation of healthcare professionals The chapter authors come from a range of countries and have experience of working in multidisciplinary clinical teams, research, and in the training of future healthcare practitioners including their development as professionals.