A previous study (ID: 80-82800-98-227) indicated that shifting care from GPs to NPs is possible in terms of safety and quality of care and resulted in cost savings due to less treatment. In that study 4 GPs and 1 NP provided care in the experimental condition and 5 GPs provided care in the control condition. Based on the results it is hypothesized that NPs are competent to diagnose and treat at least 75% of the complaints shown in out-of-hours primary care. Substituting more GPs by NPs in out-of-hours care will probably lead to more cost savings.