Background: Exercise electrocardiography (Ex-ECG) is a well-established test to evaluate patients with suspected coronary artery disease (CAD). The recent introduction of multidetector coronary computed tomographic angiography (CCTA) offers a novel noninvasive approach for evaluation of CAD. Severity of coronary artery disease on CCTA and its prognostic value have not been systematically studied in relation to Ex-ECG results. We sought to investigate whether Ex-ECG have incremental prognostic value when combined with CCTA in patients with suspected CAD.Subjects & Methods: 4,338 consecutive patients (54% male, age 60 짹 10 years) who underwent concurrent (<30 days) CCTA and Ex-ECG for the evaluation of suspected CAD from May 2003 to April 2009 were enrolled retrospectively. CCTA results were classified into 4 categories: absence of CAD; mild (<40%); moderate (40 to 70%); and severe (>70%) stenosis. Clinical follow up data were obtained for major adverse cardiac events (MACE). Patients were excluded from the analysis if they underwent elective revascularization within 60 days after index CCTA.Results: CCTA revealed absent, mild, moderate, and severe CAD in 1921 (56%), 922 (27%), 409 (12%), and 156 (5%) patients, respectively. In each group of patients, Ex-ECG were positive in 162/1921 (9%), 121/922 (13%), 75/409 (18%), and 51/156 (33%). During a mean follow-up of 704 짹 434 days, there were no significant differences in occurrence of MACEs according to Ex-ECG results in absent or severe CAD group (p=0.81, & p=0.37, respectively). However, in patients with mild or moderate CAD on CCTA, there was a significant increase in MACEs when Ex-ECG showed positive results (p<0.001, & p=0.004, respectively).Conclusions: Ex-ECG has incremental value to predict the prognosis in patients with mild to moderate coronary artery stenosis on CCTA. This is the first study to provide the outcome data demonstrating usefulness of Ex-ECG combined with CCTA in risk stratification and clinical decision making in patients with suspected CAD.