Objectives: The purpose of this study was to compare quantitative estimates of coronary calcification with traditional coronary risk factors to determine their independent predictive power for the diagnosis of obstructive angiographic coronary artery disease in symptomatic patients. Methods: Three hundred sixty-eight symptomatic patients underwent coronary angiography and electron beam computed tomography at four different centers between April 1989 and December 1993. A blinded cardiologist interpreted the electron beam computed tomograms. Coronary risk factors were obtained in all 368 patients. Both bivariate and multivariate analyses were used to investigate the relation between risk factors and angiographic disease. Results: One hundred fifty-eight patients (43%) had angiographically obstructive coronary artery disease (>50% luminal stenosis) and 297 (81%) had coronary calcification. At the bivariate level, only male sex and log-transformed coronary calcification were predictive of angiographic disease (p = 0.008, p = 0.001). By multivariate analysis, only male sex and coronary calcification were predictive (p = 0.001, p = 0.001). Sixty-four of the 71 patients without coronary calcification did not have disease, yielding a negative predictive value of 90%. Receiver operating characteristic curve analysis showed that the amount of coronary calcium was a significantly better discriminator of disease than were the other risk factors. Conclusions: Coronary calcification is a stronger predictor of angiographic coronary artery disease in symptomatic patients undergoing angiography than are standard risk factors. (Am Heart J 1998;135:696-702.)