This study was designed to determine whether a quantitative analysis of integrated backscatter amplitude distribution is potentially useful in characterizing the atherosclerotic lesion. One hundred measurements (10 x 10 array) were made in fresh aortic regions (2 cm X 2 cm) of nine normal and 19 atherosclerotic arterial walls. A 10 MHz transducer was used. The integrated backscatter distinguished normal from atherosclerotic specimens (−56.7 + 4.3 vs −42.5 + 8.9 dB, p < .01). The shape of the integrated backscatter amplitude distribution was analyzed by calculation of skewness and kurtosis of each arterial region. Both skewness values (0.134 + 0.325 vs − 0.193 + 0.491 in normal and atherosclerotic segments, respectively, p = NS) and kurtosis values (0.055 0.765 vs −0.610 0.379, p < .01) discriminated between the two groups. When only the six atherosclerotic specimens with mostly fatty and fibrofatty sites were considered, skewness and kurtosis still distinguished normal from atherosclerotic regions (0. 134 0.325 vs −0.404 + 0.232, p < .05 and 0.055 + 0.765 vs −0.558 ± 0.337, p < .05, respectively), while integrated backscatter values did not (−56.7 ± 4.5 vs −52.3 ± 6.1 dB, p = NS). In conclusion, atherosclerosis may be detected in vitro by the quantitative analysis of integrated backscatter distribution. This variable could also be of help in the identification of less obvious forms of atherosclerotic disease that are not distinguishable on the basis of integrated backscatter amplitude.