Coronary artery calcium (CAC) testing occupies a sweet spot in preventive cardiology: it is quick, inexpensive, easy to interpret, and both specific and sensitive for clinically relevant coronary atherosclerosis. Yet the ability to separate true zero from nonzero scores, the central distinction that makes CAC so powerful, also raises questions about how we should interpret the growing evidence around low (0–100), ultralow (0.1–0.9) and subthreshold CAC scores.