Unlike ST-segment elevation myocardial infarction, the degree of stenosis and physiology of ischemia varies in patients with non-ST-segment elevation myocardial infarction (NSTEMI). The prevalence, predictors, and outcomes of patients with NSTEMI who lack significant epicardial coronary artery disease (CAD) in routine clinical practice remain poorly characterized. We sought to determine the prevalence, predictors, and outcomes of patients with NSTEMI and insignificant CAD. We analyzed 38301 patients with NSTEMI in the CRUSADE quality improvement initiative who underwent cardiac catheterization to determine the prevalence and factors associated with insignificant CAD (all coronary stenoses <50%) and inhospital outcomes for patients with and without CAD. A multivariable model was used to determine the factors associated with insignificant CAD. A total of 3306 (8.6%) of 38301 patients had insignificant CAD. The strongest multivariable predictors of insignificant CAD were female sex (odds ratio 2.8, 95% CI 2.6-3.1), younger age (odds ratio per 10-year decrease 1.5, 95% CI 1.5-1.6), and lack of current/recent smoking (odds ratio 1.9, 95% CI 1.7-2.0). Inhospital rates of death were 0.65% for patients with insignificant CAD compared with 2.36% for patients with CAD (P < .0001). Insignificant CAD is present in 9% of patients with NSTEMI and is associated with a low incidence of adverse outcomes. The strongest predictors of insignificant CAD are female sex and younger age. These findings underscore the need for research to understand the pathophysiology of myocardial infarction in this population.