In this paper we describe a method (the Behaviour Change Project) for teaching 'behaviour change' principles to medical students. The project involved their changing a self-identified aspect of their own behaviour. In evaluating the project by an anonymous questionnaire (response rate 84%), most students reported enjoying the project and found it helpful in some way, particularly in learning about their own behaviour and the processes of behaviour change. While nearly all listed positive outcomes for themselves or others, some also listed negative outcomes or difficulties, such as in measuring behaviours related to clinical work. Possible extensions of the project are discussed, including its application to improving relationships with patients, increasing tolerance, strengthening ethical behaviour in clinical or research contexts, and in training specific clinical skills.