PROJECT SUMMARY/ABSTRACT There are ~1.4 million adults with congenital heart disease (ACHD) in the US and their number is increasing by 40,000-50,000/year due to improving pediatric CHD care. Up to 85% of the ACHD patients fail to establish or maintain ACHD specialist care which results in poor outcomes, the most vulnerable period for these gaps being at the time of transition and transfer from pediatric to adult healthcare. Transition includes fostering of patients’ knowledge of their CHD and of self-management and self-efficacy skills needed for lifelong management of chronic disease. Transfer is the event when a patient's care is taken over by the adult healthcare team. Since chronic management of CHD interferes with daily life activities (such as job, family planning, traveling), it is difficult for many of these adults to engage in their own care. Knowledge, self-management, self- efficacy, and patient activation are important skills for patient engagement, and strategies that enhance these skills are known to reduce gaps in ACHD care. Majority of the ACHD patients are young and own smartphones. This provides a unique opportunity to use mobile app-based intervention as a relatively inexpensive and scalable solution to support ACHD patient engagement skills. But, for its success, it is critical to incorporate theory of behavior change into its design. Thus, my central hypothesis is that an automated, interactive, mobile app-based intervention refined using ‘Capability, Opportunity, Motivation-Behavioral’ theory to evaluate the determinants of behavior can enhance skills known to support ACHD patient engagement and ACHD specialist visit. To test this hypothesis, Aim 1 will shed light on the pertinent features of a mobile app to support patient engagement skills using semi-structured interviews of the ACHD patients, clinicians, researchers, and clinic staff. Aim 2 will use an iterative process with inputs from an Advisory Board of ACHD patients, clinicians, and researchers to design and revise an automated interactive user-friendly app. Aim 3 will carry out a pilot study to determine feasibility and acceptability of the mobile app to enhance ACHD patient engagement skills. These aims will create foundational knowledge for future studies to determine effectiveness of a mHealth based intervention to support ACHD patient engagement and ensure ACHD specialist visit. Candidate is an ACHD cardiologist and health services researcher at UCSF. The candidate, her mentors and her scientific advisors have developed a comprehensive career development plan that includes training in mHealth-based behavioral interventions, qualitative methods, and clinical trials. With strong institutional commitment, the candidate is well-positioned to attain research independence.