There is a strain on primary health care whose challenges are recognised as increasing demands for care due to an ageing population, and reforms that shift care from hospitals to the community. In the face of these developments, tasks have increasingly been delegated to other staff. This thesis shows that shifting certain tasks from general practitioners (GPs) to nurse practitioners results in at least equal patient outcomes. In primary care during out-of-hours was almost 80% of the patients suitable for nurse practitioner care. Collaboration between NPs and GPs was important to treat all patients within the targeted time period. With the deployment of nurse practitioners are general practitioners able to focus on the most vulnerable and complex patients. Moreover, nurse practitioners can add additional tasks to primary care as a response to changing patient needs. A shared vision from professional associations on the nurse practitioner role in primary care is a requirement for successful implementation.