The aim of this in vitro study was to analyze the diagnostic performance of intravascular ultrasound (IVUS) in vessel wall calcifications and to compare the accuracy of mechanical 12.5 and 20 MHz transducers. Fourty-three sections of 10 vessels with signs of arteriosclerotic disease on pathologic examination were examined. Slices 500 microns thick were obtained and examined radiographically at 9 fold magnification. In each section, identical segments were defined, amounting to a total of 344 segments. The IVUS sections were analyzed by 3 experienced readers. For statistical evaluation ROC analysis was performed using magnification radiography as a reference. An area under the curve (AUC) of 0.79 was obtained for the 12.5 transducer and of 0.83 for the 20 MHz transducer. Additionally, sensitivity, specificity, and accuracy were determined. Sensitivity depended on the morphology, size, and density of the calcified lesions. We therefore conclude that the sensitivity of intravascular ultrasound concerning calcified arteriosclerotic plaques is limited and that there is no significant (p < 0.01) difference between mechanical 20 and 12.5 MHz transducers in examining iliac arteries.