OBJECTIVE The 2013 American College of Cardiology (ACC)/American Heart Association (AHA) cholesterol treatment guideline recommends monitoring percent reduction in low-density lipoprotein cholesterol (LDL-C) among patients initiating statins as an indication of response and adherence. We examined LDL-C reduction and statin adherence among high-risk patients initiating statins in a real-world setting. METHODS Retrospective cohort study. METHODS The study population included Kaiser Permanente Georgia members (n = 1066) with a history of coronary heart disease or risk equivalent(s) initiating statins in 2011. Percent change in LDL-C was defined using measurements before and 60 to 450 days after statin initiation. Statin adherence was defined by proportion of days covered, categorized as high (≥80%), intermediate (50%-79%), and low (< 50%). RESULTS Overall, 58.4% of patients failed to achieve a ≥ 30% LDL-C reduction after statin initiation. The prevalences of high, intermediate, and low statin adherence were 41.3%, 23.2%, and 35.6%, respectively. Of patients with high adherence, 42.3% did not achieve a ≥ 30% reduction in LDL-C compared with 54.7% and 79.7% of those with intermediate and low statin adherence, respectively. After multivariable adjustment, and compared with those with high adherence, the risk ratios for not achieving a ≥ 30% LDL-C reduction were 1.31 (95% CI, 1.13-1.52) and 1.88 (95% CI, 1.67-2.11), for those with intermediate and low adherence. Women and African Americans were less likely to have high adherence, whereas having cardiologist visits was associated with high adherence. CONCLUSIONS In a real-world setting, many patients did not achieve a 30% or larger LDL-C reduction. These data support the ACC/AHA recommendation to monitor LDL-C response among patients initiating statins.