Background: High-sensitivity assays can quantify cardiac troponin I concentrations in nearly all individuals. We determined whether cardiac troponin can improve our estimation of the pre-test probability for obstructive coronary artery disease in patients with suspected stable angina. Methods: In a pre-specified sub-study of the Scottish COmputed Tomography of the Heart (SCOT-HEART) trial, plasma cardiac troponin I was measured using a high-sensitivity single molecule counting assay (Singulex) in 943 adults with suspected stable angina who had undergone coronary computed tomography angiography. Rates of obstructive coronary artery disease (diameter stenosis ≥50% in ≥1 major epicardial vessel) were compared with the pre-test probability determined by the European Society of Cardiology (ESC) Coronary Artery Disease Consortium risk model with and without cardiac troponin concentrations. Results: Higher cardiac troponin concentrations were associated with obstructive coronary artery disease with a 5-fold increase across quintiles (9 to 48%, p < 0.001) independent of known cardiovascular risk factors (odds ratio [OR] 1.35 [95% confidence interval (CI) 1.25-1.46] per doubling of troponin). Cardiac troponin concentrations improved the discrimination of the ESC model for identifying obstructive coronary artery disease (c-statistic 0.785 to 0.800, p < 0.003) and improved classification into ESC-recommended categories of clinical risk (net reclassification improvement 0.143 [95% CI, 0.093-0.193]). Conclusions: High-sensitivity cardiac troponin I concentration is an independent predictor of obstructive coronary artery disease in patients with suspected stable angina. Use of this test may improve the selection of patients for further investigation and treatment.