Adolescents with solid organ transplants have poorer outcomes than adults, and do not respond as well to post-rejection treatment. In addition to well-recognized declines in individual health-related quality of life, premature graft loss creates considerable health and economic burdens. High nonadherence rates among adolescents are believed to contribute majorly to rejection, premature allograft dysfunction and failure. Studies suggest that a telephone-based peer mentoring approach, with texting and e-communication, is a promising, practical means to promote medication adherence in adolescent solid organ transplant recipients. The study's main objectives are 1) to determine the efficacy of peer mentoring to improve medication adherence and health-related quality of life vs. usual care in adolescents and young adults with solid organ transplants, and 2) to determine the mechanisms through which peer mentoring impacts medication adherence and health-related quality of life.