Evidence based medicine has had an increasing impact on primary care over the last few years. In the UK it has influenced the development of guidelines and quality standards for clinical practice and the allocation of resources for drug treatments and other interventions. It has informed the thinking around patient involvement in decision making with the concept of evidence based patient choice. There are, however, concerns among primary care clinicians that evidence based medicine is not always relevant to primary care and that undue emphasis placed on it can lead to conflict with a clinician's duty of care and respect for patient autonomy. In this paper we consider the impact of evidence based medicine on primary care, and the ethical implications of its increasing prominence for clinicians and managers in primary care.