Health systems have recently started to activate patient-facing application programming interfaces (APIs) to facilitate patient access to health data and other interactions.This study sought to ascertain health systems' understanding, strategies, governance, and organizational infrastructure around patient-facing APIs, as well as their business drivers and barriers, to facilitate national learning, policy, and progress toward adoption.We performed content analysis of semi-structured interviews with a convenience sample of 10 health systems known to be leading adopters of health technology, having either implemented or planning to implement patient-facing APIs.Eight of the ten health systems had operational patient-facing APIs, with organizational strategy driven most by federal policy, the emergence of Apple Health Records, and feelings of ethical obligation. The two priority use cases identified were enablement of a patient's longitudinal health record and digital interactions with the health system. The themes most frequently cited as barriers to increased use of patient-facing APIs were security concerns, an immature app ecosystem that does not currently offer superior functionality compared to widely-adopted electronic health record (EHR)-tethered portals, lack of business drivers, EHR-vendor hesitation toward data sharing, and immature technology and standards.Our findings reveal heterogeneity in health system understanding and approaches to implementation and use of patient-facing APIs. Ongoing study, targeted policy interventions, and sharing of best practices appear necessary to achieve successful national implementation.