Sudden cardiac death (SCD) in the adult-elderly population is mostly arrhythmic due to acute thrombotic coronary artery occlusion or chronic ischemic heart disease. In the young atherosclerotic coronary artery disease (CAD) is thought to play a negligible role. We reviewed our pathology experience (1980–2016) in 690 consecutive SCDs in the young (≤40 years old, sudden infant death excluded). We found that CAD was the major cause of SCD (18%). It was observed in 125 subjects (mean age 32.3 ± 5.3 years, female 14), with a peak in 31–40 years old age interval. Site, extent, and histologic type of CAD were peculiar: single plaque of the proximal left anterior descending coronary artery, consisting of fibrocellular proliferation, with rare lipid core. The culprit atherosclerotic segment showed critical stenosis in 66% of cases and thrombotic occlusion in 34%, the latter as the consequence of plaque rupture in 47% and plaque erosion in 53%, which occurred even upon noncritical stenosis. An overt histologically acute myocardial infarction was never seen. When SCD took place during Holter monitory, transient myocardial ischemia was recorded, followed by ventricular fibrillation at the time of reperfusion. Atherosclerotic CAD was found to be the major cause of SCD also in the young, precipitated by acute coronary thrombosis in only a third of cases, more frequently upon endothelial erosion. Functional plaque instability with vasospasm, superimposed to a critical coronary plaque with ECG transient myocardial ischemia, was observed to precipitate SCD.