Background. The purpose of this study was to compare the incremental value of clinical information, electrocardiographic data, myocardial perfusion imaging, and radionuclide angiography for predicting severe coronary artery disease at a single testing interval. Clinical information, treadmill exercise studies, radionuclide angiography, and myocardial perfusion imaging are important predictors of severe coronary artery disease. However, the relative and absolute diagnostic importance of each of these methods has not been addressed at a single testing interval. Methods and Results. A same-day rest/treadmill exercise perfusion and function study was performed in 167 patients within 90 days of coronary angiography. A multivariable regression model was used to assess the independent informational content of these predictors. Clinical and electrocardiographic data were related strongly to the presence of severe coronary artery disease ( ξ 2 = 12.2 and p < 0.001; ξ 2 = 11.8 and p < 0.001, respectively). Combined perfusion and functional studies contributed 31% of the diagnostic information beyond that provided by clinical and electrocardiographic data alone ( p < 0.05). Conclusions. These data demonstrate that combined studies of myocardial perfusion and left ventricular function are able to improve prediction of the extent of coronary artery disease, even when clinical and electrocardiographic data are also available.