Low antihypertensive medication adherence is common. During recent years, the impact of low medication adherence on increased morbidity and healthcare costs has become more recognized, leading to interventions aimed at improving adherence. We analyzed a 5% sample of Medicare beneficiaries initiating antihypertensive medication between 2007 and 2012 to assess whether reductions occurred in discontinuation and low adherence. Discontinuation was defined as having no days of antihypertensive medication supply for the final 90 days of the 365 days after initiation. Low adherence was defined as having a proportion of days covered <80% during the 365 days after initiation among beneficiaries who did not discontinue treatment. Between 2007 and 2012, 41 135 Medicare beneficiaries in the 5% sample initiated antihypertensive medication. Discontinuation was stable during the study period (21.0% in 2007 and 21.3% in 2012; P-trend=0.451). Low adherence decreased from 37.4% in 2007 to 31.7% in 2012 (P-trend<0.001). After multivariable adjustment, the relative risk of low adherence for beneficiaries initiating treatment in 2012 versus in 2007 was 0.88 (95% confidence interval, 0.83-0.92). Low adherence was more common among racial/ethnic minorities, beneficiaries with Medicaid buy-in (an indicator of low income), and those with polypharmacy, and was less common among females, beneficiaries initiating antihypertensive medication with multiple classes or a 90-day prescription fill, with dementia, a history of stroke, and those who reached the Medicare Part D coverage gap in the previous year. In conclusion, low adherence to antihypertensive medication has decreased among Medicare beneficiaries; however, rates of discontinuation and low adherence remain high.