PURPOSE: To identify characteristics and outcomes of patients who use physician assistants and nurse practitioners (PA/NPs) as a usual source of care. METHODS: Cross sectional analysis using the telephone and mail surveys of the Wisconsin Longitudinal Study (WLS), a prospective cohort study of Wisconsin high school graduates and selected siblings (n = 6,803). FINDINGS: Individuals from metropolitan (OR = 0.40, 95% CI = 0.29-0.54) and micropolitan (OR = 0.65, 95% CI = 0.44-0.95) areas were less likely to utilize PA/NPs than participants from rural locations. Participants without insurance or with public insurance other than Medicare were more likely than those with private insurance to utilize PA/NPs (OR = 1.71, 95% CI = 1.02-2.86). Patients of PA/NPs were more likely to be women (OR = 1.77, 95% CI = 1.34-2.34), younger (OR = 0.95, 95% CI = 0.92-0.98) and have lower extroversion scores (OR = 0.81, 95% CI = 0.68-0.96). Participants utilizing PA/NPs reported lower perceived access (beta=-0.22, 95% CI =-0.35-0.09) than those utilizing doctors. PA/NP utilization was associated with an increased likelihood of chiropractor visits (OR = 1.57, 95% CI = 1.15-2.15) and decreased likelihood of a complete health exams (OR = 0.74, 95% CI = 0.55-0.99) or mammograms (OR = 0.65, 95% CI = 0.45-0.93). There were no significant differences in self-rated health or difficulties/delays in receiving care. CONCLUSIONS: Populations served by PA/NPs and doctors differ demographically but not in complexity. Though perceived access to care was lower for patients of PA/NPs, there were few differences in utilization and no differences in difficulties/delays in care or outcomes. This suggests that PA/NPs are acting as primary care providers to underserved patients with a range of disease severity, findings which have important implications for policy, including clinician workforce and reimbursement issues.