Objective: The Institute of Medicine argues that the integration of primary care (PC) and public health (PH) is of paramount importance. We undertook this qualitative study to better understand how these collaborations function., Data Sources: Investigators from PC and PH practice-based research networks in Colorado, Minnesota, Washington, and Wisconsin identified 40 key informants from the PH and PC fields within their respective states., Study Design: The key informants participated in standardized, semistructured interviews., Data Collection: Coinvestigators from each state conducted telephone interviews. The interviews were recorded, transcribed, and analyzed using NVivo 10., Principal Findings: Participants described 2 main types of themes. One, which we have termed "foundational" aspects of partnership, includes leadership, communication, mutual awareness, formal processes, history and values. The other, which we have characterized as "energizing" aspects of partnerships, includes having a shared strategic vision, opportunity, and the shifting culture in PC and PH. While the vast majority of participants described the value of foundational aspects of partnership, those who reported having more active collaborations were more likely to also describe the energizing aspects of partnerships., Conclusions: Our findings indicate that interactions between foundational aspects and energizing aspects of partnerships are dynamic. Further exploration of these aspects may help us to understand how best to support the integration of PC and PH., Competing Interests: Conflict of interest: none declared., (© Copyright 2017 by the American Board of Family Medicine.)