Acute coronary syndromes (ACS) represent a major cause of morbidity and mortality for patients with cardiovascular disease, but evidence-based therapies shown to improve outcomes for ACS are often underused in clinically eligible patients. Although clinical practice guidelines have been developed to provide standards for the diagnosis and treatment of patients with ACS and to provide physicians with a framework for clinical decision-making, multiple obstacles have hindered their implementation and questions remain about the applicability of guidelines for diverse clinical situations. Systematic reviews of quality-improvement studies have shown that multifaceted approaches using targeted educational interventions, creation of quality standards, and regular performance feedback are needed to ensure sustained improvements in care. Approaches to quality improvement thus are being redirected to focus on multidisciplinary collaborations designed to improve the entire process of care for patients with ACS. Multiple large observational registries and quality-improvement initiatives now are capturing data regarding adherence to practice guidelines and contemporary patterns of care for ACS. This comprehensive evaluation of ACS treatment will help guide efforts designed to promote evidence-based care and ultimately determine the effect of widespread implementation of practice guidelines on clinical outcomes. The shifting model of care for ACS therefore suggests that quality improvement and monitoring of adherence to practice guidelines should be considered components of optimal clinical practice.