Background and Purpose— Previous studies have shown the presence of ulceration in atherosclerotic plaque either by categorizing the plaque as complex (irregular morphology with ulcers) or smooth or by quantifying the number of ulcers observed in a specific region of interest. The aim of this study was to quantify carotid total ulcer volume by 3-dimensional ultrasound to investigate the relationship of total ulcer volume to vascular events (strokes, transient ischemic attack, myocardial infarction, revascularization, or death because of cardiovascular reasons). Methods— In total, 349 at-risk subjects provided written informed consent to carotid 3-dimensional ultrasound and were analyzed for ulcerations. Ulcer volume was defined as a distinct discontinuity in an atherosclerotic plaque, with a volume ≥1.00 mm ³ as measured using manual segmentation. The sum of the volumes of all ulcers seen in both carotids was the total ulcer volume. Participants were monitored for ≤5 years for outcomes, including cardiovascular events and death. Results— Kaplan–Meier survival analysis showed that subjects with total ulcer volume ≥5 mm ³ experienced a significantly higher risk of developing stroke, transient ischemic attack, or death ( P =0.009) and of developing stroke/transient ischemic attack/death/myocardial infarction/revascularization ( P =0.017). Lower ulcer volumes did not predict events nor did ulcer depth. Conclusions— Volume of carotid ulceration on 3-dimensional ultrasound predicts cardiovascular events. In addition to improving risk stratification, ulceration is a potential therapeutic target.