The proposed research seeks to determine whether text messages/messaging (TM) or a mobile application (app), compared with an educational website-control provided to all Veterans, can improve adherence to antiplatelet therapy among patients following acute coronary syndrome or percutaneous coronary intervention (ACS/PCI). Adherence to antiplatelet medications is critical to prevent life- threatening complications (i.e., stent thrombosis); yet rates of non-adherence range from 21-57% by 12 months. Mobile technology through TM or mobile apps is a practical and inexpensive strategy to promote behavior change and enhance medication adherence. The three specific aims of this proposal are to: 1) determine preferences for content and frequency of TM to promote medication adherence through focus groups; 2) determine the most patient-centered app to promote adherence through a content analysis of all commercially available apps for medication adherence and focus groups centered on usability; and 3) compare adherence to antiplatelet medications in 225 Veterans post ACS/PCI through a randomized clinical trial. Participants will be randomized to either TM, mobile app, or website-control group. The focus groups will be stratified by low/high mobile phone use and sex. In addition, the proposed work will provide Dr. Park with the mentorship and experience necessary to establish herself as an early career investigator in the fields of cardiovascular disease prevention and mobile health research. Dr. Park's primary career goal is to become an independent nurse investigator who applies novel technology for patient-centered behavioral interventions to improve clinical outcomes and quality of life for cardiac patients and Veterans. Dr. Park has assembled an outstanding interdisciplinary team of mentors with expertise in the required areas of training. Eileen Collins, PhD, RN will serve as Primary Nurse Mentor; Mary Whooley, MD will serve as VA On-Site Mentor; and Janet Shim, PhD will serve as Qualitative Research Mentor. In addition, John Boscardin, PhD will conduct all quantitative statistical analyses related to the study. Consultants include Yoshimi Fukuoka, RN, PhD (expert in mobile health strategies) and Dr. Michael Ho (expert in medication adherence and cardiovascular disease). Susan Woods, MD, MPH (Director of Patient Experience, Connected Health, Office of Information and Analytics, VHA) will serve as a collaborator, particularly in relationship to our use of ?Annie,? the new VA automated TM program with a goal to help patients take a more active role in their health. The Nursing Research Initiative will provide Dr. Park with an exceptional opportunity to receive the mentorship and experience necessary to prepare a strong scientific foundation for a compelling Investigator Initiated Research proposal to evaluate clinical outcomes (i.e., cardiac morbidity and mortality) through a multi-site full scale RCT. Determining the efficacy of mobile technology through a Veteran-designed protocol to promote medication adherence will have a significant impact on Veteran health and public health, particularly for individuals with chronic diseases that require strict medication adherence.