Data are sparse regarding the long-term benefit of care concordant with clinical practice guidelines in patients presenting with unstable angina pectoris and non-ST-segment elevation myocardial infarction (UAP/NSTEMI), particularly in the general care setting. We extended follow-up in a preexisting cohort of 275 patients hospitalized with primary UAP/NSTEMI. Using Cox models, we compared long-term mortality between patients who received care concordant with > or =80% of 8 important guideline recommendations during the index hospitalization and patients who did not. Among all study patients, 68% received guideline-concordant care. During follow-up (median 9.4 years) 49% of patients died. Patients with UAP/NSTEMI who received guideline-concordant care had significantly decreased long-term mortality compared with those who received guideline-discordant care (hazards ratio [HR] 0.45, 95% confidence interval [CI] 0.32 to 0.64). Guideline-concordant care remained associated with decreased mortality after adjusting for other predictors of long-term mortality (HR 0.57, 95% CI 0.39 to 0.84) and after adjustment for the propensity to receive guideline-concordant care (HR 0.61, 95% CI 0.43 to 0.88). The benefit of guideline-concordant care relative to discordant care was preserved in high-risk populations shown to be less likely to receive guideline-concordant care, including patients with advanced age, congestive heart failure, elevated serum creatinine, and prior myocardial infarction. Care concordant with UAP/NSTEMI clinical practice guidelines is associated with substantially improved long-term survival. Our findings endorse the approach adopted by authors of clinical practice guidelines in generalizing evidence-based medicine to usual clinical care. In firmly establishing the benefit of consensus guidelines, the foundation is set for efforts to improve practitioner compliance with these standards.