The 2013 American College of Cardiology/American Heart Association (ACC/AHA) Cholesterol Management Guideline recommends moderate-intensity to high-intensity statin therapy in eligible patients. To examine adoption of the 2013 ACC/AHA guideline in US cardiology practices. Among 161 cardiology practices, trends in the use of moderate-intensity to high-intensity statin and nonstatin lipid-lowering therapy (LLT) were analyzed before (September 1, 2012, to November 1, 2013) and after (February 1, 2014, to April 1, 2015) publication of the 2013 ACC/AHA guideline among 4 mutually exclusive risk groups within the ACC Practice Innovation and Clinical Excellence Registry. Interrupted time series analysis was used to evaluate for differences in trend in use of moderate-intensity to high-intensity statin and nonstatin LLT use in hierarchical logistic regression models. Participants were a population-based sample of 1 105 356 preguideline patients (2 431 192 patient encounters) and 1 116 472 postguideline patients (2 377 219 patient encounters). Approximately 97% of patients had atherosclerotic cardiovascular disease (ASCVD). Moderate-intensity to high-intensity statin and nonstatin LLT use before and after publication of the 2013 ACC/AHA guideline. Time trend in the use of moderate-intensity to high-intensity statin and nonstatin LLT. In the study cohort, the mean (SD) age was 69.6 (12.1) years among 1 105 356 patients (40.2% female) before publication of the guideline and 70.0 (11.9) years among 1 116 472 patients (39.8% female) after publication of the guideline. Although there was a trend toward increasing use of moderate-intensity to high-intensity statins overall and in the ASCVD cohort, such a trend was already present before publication of the guideline. No significant difference in trend in the use of moderate-intensity to high-intensity statins was observed in other groups. The use of moderate-intensity to high-intensity statin therapy was 62.1% (before publication of the guideline) and 66.6% (after publication of the guideline) in the overall cohort, 62.7% (before publication) and 67.0% (after publication) in the ASCVD cohort, 50.6% (before publication) and 52.3% (after publication) in the cohort with elevated low-density lipoprotein cholesterol levels (ie, ≥190 mg/dL), 52.4% (before publication) and 55.2% (after publication) in the diabetes cohort, and 41.9% (before publication) and 46.9% (after publication) in the remaining group with 10-year ASCVD risk of 7.5% or higher. In hierarchical logistic regression models, there was a significant increase in the use of moderate-intensity to high-intensity statins in the overall cohort (4.8%) and in the ASCVD cohort (4.3%) (P < .01 for slope for both). There was no significant change for other risk cohorts. Nonstatin LLT use remained unchanged in the preguideline and postguideline periods in the hierarchical logistic regression models for all of the risk groups. Adoption of the 2013 ACC/AHA Cholesterol Management Guideline in cardiology practices was modest. Timely interventions are needed to improve guideline-concordant practice to reduce the burden of ASCVD.