Recent policy developments in the National Health Service, case including NHS walk­in centres, buy NHS Direct, and nurse led personal medical services schemes, have been based on nurses rather than doctors acting as first point of contact with the health service.1 2 Several factors have led to this expansion in the role of nurses, including issues of cost, the need to increase provision of care to improve access, the availability of doctors, and the skills and expertise of nurses. Particular interest has been shown in the concept of nurse practitioners providing front line care in gen­ eral practice and in emergency departments. In this way they may potentially substitute for doctors, particularly in the management of patients with acute illness. Nurse practitioners have undergone further training, often at graduate level, to work autonomously, making independent diagnoses and treatment deci­sions.3 It is important to consider whether the evidence supports the notion that nurse practitioners can substitute for doctors by providing safe, effective, and economical front line management of patients. Nurse practitioners have been established in North America for several decades, and studies of their role have been reviewed previously.4 5 But these reviews are dated and of limited applicability to the United Kingdom. After the expansion of nurse practitioners in the NHS during the 1990s, several relevant ran­ domised controlled trials have been published that directly compare nurse practitioners and doctors. We aimed to systematically review research that assesses the process, costs, or outcomes of care provided by nurse practitioners compared with doctors, working in primary care as a first point of contact for any patient with undifferentiated health problems.