Like the rest of the western world, the UK faces a significant increase in the prevalence of diseases associated with lifestyle. Smoking rates have reduced, but increasing obesity has contributed to alarming increases in diabetes. Discovery of the correlation between behaviour and poor health has, since the 1970s, resulted in public health policies emphasising behaviour change, and personal responsibility; an emphasis that survived later research which demonstrated social, genetic and psychological determinants on behaviour and health. The latest version of the NHS constitution exhorts us to 'recognise that you can make a significant contribution to your own, and your family's, good health and wellbeing, and take personal responsibility for it.' This thesis seeks to clarify the meaning and extent of personal responsibility for health, and at its core are four papers published in peer-reviewed journals. The first clarifies the concept concluding that it is best understood in a tripartite conception of a moral agent having obligations and being held responsible if he fails to meet them. The following two papers discuss the nature of the obligations, using utilitarian reasoning and arguments from analogy. First, an exploration of the moral obligations for our own health is undertaken via an analysis of the practice of tombstoning, jumping from height into water. I conclude that the obligations are of process rather than outcome, consisting of an epistemic duty to determine the health related consequences of our acts, and a reflective duty to consider these consequences for us and for those who share our lives. Second, following an examination of the moral status of blood donation, I conclude that despite its presentation as a praiseworthy and supererogatory act, it is more properly regarded as a prima facie obligation, supported by arguments from beneficence and justice. The final paper discusses the final part of the tripartite conception of personal responsibility for health: being held responsible. I discuss the nature of blame and extend the tombstoning analogy as a way of testing my own intuitions in response to an imagined adult son who has undertaken this dangerous activity. I argue that the notion of blame is not generally allowed as part of the patient - professional relationship, and yet without considering blame, the concept of personal responsibility for health is incomplete. I conclude that if the epistemic and reflective duties, individually applied, conclude that an obligation is owed, it is owed to those within personal relationships, and holding people responsible for their health-effecting behaviour is also best undertaken within these relationships.I conclude the thesis by considering the implications for professional practice. Inevitably this leads to consideration of the promotion of personal autonomy in health care. A more relational account of autonomy is suggested. Facilitating the epistemic duty so that individuals are better able to understand the risks of their behaviour requires rethinking of the way that health promoting material and information are presented.