Background: Coronary atherosclerosis may develop at an early age and remain latent for many years. Objective: To define characteristics of subclinical coronary atherosclerosis associated with the development of myocardial infarction. Design: Prospective observational cohort study. Setting: Copenhagen General Population Study, Denmark. Participants: 9533 asymptomatic persons aged 40 years or older without known ischemic heart disease. Measurements: Subclinical coronary atherosclerosis was assessed with coronary computed tomography angiography conducted blinded to treatment and outcomes. Coronary atherosclerosis was characterized according to luminal obstruction (nonobstructive or obstructive [≥50% luminal stenosis]) and extent (nonextensive or extensive [one third or more of the coronary tree]). The primary outcome was myocardial infarction, and the secondary outcome was a composite of death or myocardial infarction. Results: A total of 5114 (54%) persons had no subclinical coronary atherosclerosis, 3483 (36%) had nonobstructive disease, and 936 (10%) had obstructive disease. Within a median follow-up of 3.5 years (range, 0.1 to 8.9 years), 193 persons died and 71 had myocardial infarction. The risk for myocardial infarction was increased in persons with obstructive (adjusted relative risk, 9.19 [95% CI, 4.49 to 18.11]) and extensive (7.65 [CI, 3.53 to 16.57]) disease. The highest risk for myocardial infarction was noted in persons with obstructive-extensive subclinical coronary atherosclerosis (adjusted relative risk, 12.48 [CI, 5.50 to 28.12]) or obstructive-nonextensive (adjusted relative risk, 8.28 [CI, 3.75 to 18.32]). The risk for the composite end point of death or myocardial infarction was increased in persons with extensive disease, regardless of degree of obstruction - for example, nonobstructive-extensive (adjusted relative risk, 2.70 [CI, 1.72 to 4.25]) and obstructive-extensive (adjusted relative risk, 3.15 [CI, 2.05 to 4.83]). Limitation: Mostly White persons were studied. Conclusion: In asymptomatic persons, subclinical, obstructive coronary atherosclerosis is associated with a more than 8-fold elevated risk for myocardial infarction.