Background: The extent of coronary artery calcification (CAC) and near-term adverse clinical outcomes are strongly related through 5 years of follow-up. Objective: To describe the ability of CAC scores to predict long-term mortality in persons without symptoms of coronary artery disease. Design: Observational cohort. Setting: Single-center, outpatient cardiology laboratory. Patients: 9715 asymptomatic patients. Measurements: Coronary artery calcification scoring and binary risk factor data were collected. The primary end point was time to all-cause mortality (median follow-up, 14.6 years). Univariable and multivariable Cox proportional hazards models were used to compare survival distributions. The net reclassification improvement statistic was calculated. Results: In Cox models adjusted for risk factors for coronary artery disease, the CAC score was highly predictive of all-cause mortality (P < 0.001). Overall 15-year mortality rates ranged from 3% to 28% for CAC scores from 0 to 1000 or greater (P < 0.001). The relative hazard for all-cause mortality ranged from 1.68 for a CAC score of 1 to 10 (P < 0.001) to 6.26 for a score of 1000 or greater (P < 0.001). The categorical net reclassification improvement using cut points of less than 7.5% to 22.5% or greater was 0.21 (95% CI, 0.16 to 0.32). Limitations: Data collection was limited to a single center with generalizability limitations. Only binary risk factor data were available, and CAC was only measured once. Conclusion: The extent of CAC accurately predicts 15-year mortality in a large cohort of asymptomatic patients. Long-term estimates of mortality provide a unique opportunity to examine the value of novel biomarkers, such as CAC, in estimating important patient outcomes.