A noninvasive method based on high-resolution B-mode ultrasonography and a computerized image-analyzing system were used for the quantification of early (thickening of the intima-media complex) and late (plaque) atherosclerosis in the carotid and the femoral artery. The difference between repeated measurements was assessed to estimate intraobserver and inter-observer differences. The results were satisfactory, with a coefficient of variation for measurement of lumen diameter in the common carotid artery of 3.8 +/- 4.1% (r = 0.91) and for the femoral artery of 4.8 +/- 4.1% (r = 0.93). Corresponding figures for intima-media thickness in the common carotid artery and the femoral artery were 10.0 +/- 8.5% (r = 0.86) and 16.2 +/- 12.6% (r = 0.91), respectively. The coefficient of variation for measurements of maximal intima-media thickness at the site of the plaque was 14.6 +/- 10.5% (r = 0.88); for plaque base, 13.1 +/- 9.0% (r = 0.91); and for plaque area, 16.3 +/- 12.6% (r = 0.90). The method seems promising for the detection and quantification of early and late atherosclerotic lesions in the carotid and femoral arteries.