506C ardiovascular diseases (CVDs) are a leading cause of death in the world. High blood pressure contributes to ≈54% of stroke and 47% of IHD worldwide.1 Managing blood pressure in hypertensive patients is important for the prevention of CVD and the reduction of mortality. 2,3 The use of antihypertensive drug therapy reduces the risk of stroke by an estimated 34% and the risk of IHD by 21%. 4 The definition of medication adherence is that patients take their medications as prescribed, as well as continuing to take a prescribed medication based on the treatment alliance established between the patient and the physician. 5 Adherence to medication among patients with chronic diseases is suboptimal, dropping most dramatically during the first year after the start of therapy. 6,7 For example, half of the patients who are prescribed an antihypertensive drug will discontinue their medication within 1 year of starting the therapy. [8][9][10] Patients with chronic diseases require a good partnership with their physician in order to achieve the long-term outcome goal. Patients who are adherent to antihypertensive drugs are more likely to achieve blood pressure control. A meta-analysis reported that patients adherent to antihypertensive medications showed better blood pressure control, compared with those who were nonadherent (odds ratio, 3.44; 95% confidence interval [CI], 1.60-7.37).11 Evidence is mounting that patients who show poor adherence to antihypertensive medication have a higher risk of adverse outcomes, including allcause hospitalization and CVD hospitalization, 12,13 and they have higher healthcare costs 14 compared with patients with good adherence. 12,13,15 A recent cohort study 15 reported that a good-adherence group had a significantly lower incidence of acute cardiovascular events, compared with a group with poor adherence to antihypertension medication (hazard ratio [HR], Abstract-The importance of adherence to antihypertensive treatments for the prevention of cardiovascular disease has not been well elucidated. This study evaluated the effect of antihypertensive medication adherence on specific cardiovascular disease mortality (ischemic heart disease [IHD], cerebral hemorrhage, and cerebral infarction). Our study used data from a 3% sample cohort that was randomly extracted from enrollees of Korean National Health Insurance. Study subjects were aged ≥20 years, were diagnosed with hypertension, and started newly prescribed antihypertensive medication in 2003 to 2004. Adherence to antihypertensive medication was estimated as the cumulative medication adherence. Subjects were divided into good (cumulative medication adherence, ≥80%), intermediate (cumulative medication adherence, 50%-80%), and poor (cumulative medication adherence, <50%) adherence groups. We used time-dependent Cox proportional hazards models to evaluate the association between medication adherence and health outcomes. Among 33 728 eligible subjects, 670 (1.99%) died of coronary heart disease or stroke during follow-up. Patients with poor...