We conducted an observational study relating the occurrence of acute myocardial infarction (MI) to coronary artery calcium progression in 817 asymptomatic subjects referred for sequential electron beam tomographic imaging (average interval 2.2 +/- 1.3 years). A calcium volume score (CVS) was used for plaque quantification. The yearly mean absolute and percent CVS changes in the 45 patients who had a MI were 147 +/- 152 and 47 +/- 50%, respectively, compared with 63 +/- 128 and 26 +/- 32%, respectively (p <0.001, p = 0.01), in patients without events.