Controlling the overall cost of medical care requires controlling the number of physician visits. Nurse practitioners and physician assistants (NPs/PAs) may function as lower-cost substitutes for physicians or they may complement physician services. The association between NP/PA and physician visits when NPs/PAs are not working as primary care providers (PCPs) has not been thoroughly studied. A sample of 400 family medicine patients drawn from 1 large multisite practice was studied using multiple logistic regression analysis. NPs/PAs did not function as PCPs during the study period. Patients were defined as outliers if they visited physicians more than 5 times in a year. Patients who visited NPs/PAs in non-retail clinics were significantly more likely to be physician visit outliers. Visits to NPs/PAs in retail clinics were not related to physician visits. NP/PA visits in standard medical office settings complement physician visits when the NPs/PAs were not working as PCPs in this large multisite practice. Health care reform proposals relying on increased use of NPs/PAs may be more cost-efficient if NPs/PAs are located in retail settings or function as PCPs.