Background-Preceding release of the 2013 American College of Cardiology (ACC)/American Heart Association (AHA) cholesterol guidelines, prescribers aimed for specific low-density lipoprotein cholesterol (LDL-C) goals in patients with atherosclerotic cardiovascular disease (ASCVD). The 2013 guidelines changed this focus to treating patients with appropriate statin intensity given their ASCVD risk. We examined statin use and LDL-C levels before and after the 2013 ACC/AHA guidelines in patients with clinical ASCVD as defined in the guidelines. Methods and Results-We conducted a retrospective cohort study of adult commercial and Medicare Advantage health plan enrollees in the Optum Research Database. Patients had >= 1 claim with a diagnosis of clinical ASCVD between November 1, 2012 and December 31, 2014 and were continuously enrolled 6 months before (baseline) and 7 months after (follow-up) the first ASCVD visit. Patients were assigned to monthly cohorts based on ASCVD event month. Statin use and intensity were measured at baseline and first month of follow-up. LDL-C changes were assessed using ordinary least squares regression. For 90 287 patients, mean (SD) age was 68 (12) years; 50% were female; and 30% had commercial insurance. Statin use remained consistent before and after guidelines (32% and 31%, respectively). Of patients receiving statins, high-intensity use increased by 4 percentage points 1 year after guidelines (P< 0.001). Mean LDL-C levels were 2.4 mmol/L (94 mg/dL) both pre-and postguidelines. Conclusions-Statin use and mean monthly LDL-C before and after the guidelines remained largely unchanged; statin intensity increased modestly. More effort may be needed to increase guideline understanding and adherence to improve treatment of highrisk patients.