Background: Medication adherence is crucial for positive outcomes in the management of chronic conditions. Purpose: To determine variables that impact self-reported medication adherence behaviors in an ambulatory Medicare population. Methods: Twelve community health fairs targeting Medicare beneficiaries were held in cities across Central/Northern California during the 2013 Medicare open enrollment period. Beneficiaries' demographic and health information were collected and responses to survey questions regarding medication adherence behaviors documented. Survey questions addressed how often medication is taken as directed; and if not taken as directed, the reasons were recorded. Demographic, socioeconomic and health-related factors were evaluated to see if reported adherence behaviors differed as a function of these variables. Results: Of the 647 beneficiaries who were offered Medication Therapy Management services, 574 completed the adherence questions. Of responders, 406 (70%) reported complying with medications all of the time. One hundred sixty-nine (30%) provided reasons for non-adherence, of which 73% forget to take medications, 11% did not take medications due to side effects and 10% did not think the medication was needed. Lower self-reported adherence rates are associated with difficulty paying for medication (p=0.01), presence of a medication-related problem (p=0.008), and self-reported asthma (p=0.007), allergic rhinitis (p=0.002), gastro-esophageal reflux disease (p=0.005) or anxiety (p=0.01). Conclusions: Improved medication adherence is essential for optimal therapeutic outcomes in Medicare beneficiaries. Mechanisms to enhance adherence include medication reminders, elimination of cost barriers, identification and resolution of side effects or other medication-related problems and improved education about pharmacologic management of chronic conditions.