The objective of this study was to measure the interobserver and interscan variation of coronary artery calcium scores using multidetector-row computed tomography (MDCT). Seventy-five patients underwent 2 sequential MDCT scans for coronary artery calcification. Each patient's score was separately measured by 3-blinded radiologists. Scores were treated as discrete and continuous data, and independent statistical analysis was performed on all results. There was a high proportion of interscan and inter-reader concordance for the presence of coronary calcium (range, 0.893-0.973) and for its quantity (range, 0.936-0.988). Overall, prospectively triggered multidetector-row calcium scoring is reproducible though there is more variation in those patients with already high scores. There is no need to scan patients twice at the same sitting.