This dissertation addressed the contributions of primary care nurses (PCNs) to primary care and the economic returns to their human capital. Human capital theory was used to derive a conceptual framework that provided guidance for the three analyses conducted in this dissertation. The first analysis was an integrative literature review of PCNs’ contributions to primary care, including the care they provide and the outcomes of their care. The second analysis compared the care provided by PCNs and primary care physicians (PCPs), including their functions, roles, and the diagnostic characteristics of their care recipients. The third analysis compared the wages of primary care nurse practitioners (PCNPs) working in primary care settings with those working in specialty care settings. The findings of the first analysis indicate that PCNs perform a wide range of functions, serve in substitute, supplemental, and other roles, and manage patients with a variety of diagnoses. With respect to the outcomes of PCN care, the findings indicate that PCNs have improved the effectiveness and patient-centeredness of primary care, but that evidence is lacking with respect to the safety, timeliness, efficiency, and equity of primary care. The findings of the second analysis indicate that PCNs were more likely to provide therapeutic care but less likely to provide diagnostic care than PCPs. Moreover, when PCNs served in a substitute role for PCPs, they managed patients with similar diagnoses as those managed by PCPs, and when PCNs and PCPs served in supplemental roles, they managed patients with different diagnoses. Finally, findings from the third analysis indicate that PCNPs working in primary care settings earned, on average, $4.07 per hour less than PCNPs working in specialty care settings, and this wage disparity was largely due to unobserved or unexplained factors. The findings of this dissertation provide guidance for future research focusing on PCNs’ contributions to primary care and the economic returns to their human capital. Organizational leaders, educators, and policymakers can use these findings to develop approaches and policies that address how PCNs’ human capital is best used in the changing primary care system and in meeting the increased demand for primary care.