OBJECTIVE To assess reproducibility of coronary calcium measurements with Multi Detector-Row Computed Tomography (MDCT) imaging and to evaluate whether different measurement protocols, slice thickness, and cardiovascular risk factors affect inter and intra-observer reproducibility. STUDY DESIGN AND SETTING In a cross-sectional design, the study population comprised 199 healthy postmenopausal women. Coronary calcium was assessed using a 16-MDCT (Philips Mx 8000 IDT 16). Images were made using 1.5 and 3.0mm slice thicknesses. To assess inter and intra-observer reproducibility, the images were read by two observers. One observer read the images of 52 subjects twice. The Agatston score, a volume, and a mass measurement were used to quantify coronary calcium. Reproducibility was determined by estimation of mean, absolute, and relative differences between scores of the observers and by estimation of intraclass correlation coefficients (ICC). RESULTS 60.3% participants (n=120) had a positive calcium score. Median Agatston score for the first observer was 2.20 with a range of 0-2,019. The reproducibility of coronary calcium measurements between and within observers was excellent with ICC of >0.95, and small mean, absolute, and relative differences. Reproducibility findings were similar for 1.5mm slices as for 3.0mm slices, and equal for Agatston, volume, and mass measurements. CONCLUSION Reproducibilility of coronary calcium measurement using MDCT is excellent, irrespective of slice thickness and type of calcium parameter.