OBJECTIVES: To examine statin adherence and persistence among patients receiving treatment for secondary prevention of coronary heart disease (CHD) at US Military Treatment Facilities (MTF) within the Department of Defense (DoD). METHODS: Retrospective cohort study utilizing the DoD Military Health System database to examine 21,053 TRICARE beneficiaries between 18-75 years of age, receiving medical services for a primary CHD event at an MTF between January 1, 2004 and December 31, 2008. Drug adherence was measured using the Medication Possession Ratio (MPR) at 6, 12 and 18 months. Persistence was measured as duration of statin-therapy based on ≥35-day refill gap. Covariates included age, gender, comorbidities, drug-switching and dosage titration. Logistic regression was conducted to assess predictors of adherence [95% Confidence-Intervals]. RESULTS: The CHD cohort (N=21,053) was 74% male with a mean age of 57.4(SD=8.8) years. Overall mean MPR was 89%(SD=22) at month six (M6), 84%(SD=25) at 12-months (M12), and 81%(SD=26.4) after 18-months (M18). Approximately 80% of patients were adherent (MPR≥80%) with statin-therapy at M6 which declined to 71% at M12, and 69% at the end of M18 (p<.001). Older male patients with hyperlipidemia were more adherent. Adjusting for covariates, patients were more likely to be adherent at M6, M12, and M18 that switched statins  (OR=1.87[1.65-2.13],1.3[1.24-1.46], and 1.07[1.00-1.15]) or had at least one titration adjustment (OR=2.99[2.62-3.40],1.86 [1.72-2.01], and 1.54[1.44-1.65]) compared to patients with no therapeutic adjustments. Overall mean persistence to statins was 322 days. Patients experiencing ≥35-day refill gap increased from 34% to 53% to 63% at 6, 12, and 18-months respectively. CONCLUSIONS: This study showed statin adherence was high among DoD patients receiving medical care at MTFs for secondary prevention of CHD during the first 6-months. Adherence and persistence, however, declined by month 12. Improved patient adherence was associated with closer monitoring of prescribed therapy, as seen among patients who were titrated or switched statins.