Two morphological methods for quantifying the degree of stenoses in the iliac arteries, intravascular ultrasound (IVUS) and arteriography, were compared with duplex scanning, a method of evaluating the haemodynamic importance of the stenosis. A total of 38 patients, 20 women and 18 men, median age 66 y, admitted for either PTA (n=18) or femoro-femoral crossover bypass surgery (n=20), were examined by IVUS, single plane arteriography and duplex scanning. The predictive value, sensitivity, specificity and kappa value of IVUS were higher than the corresponding values for arteriography. Logistic regression analysis found that IVUS had a predictive value (p=0.0003) for diagnosing significant stenosis as defined by duplex scanning, but arteriography did not (p=0.1). However, this difference in usefulness as predictors did not reach significance. The agreement between arteriography and IVUS was relatively good. The conclusion is that IVUS seems to be superior to single-plane arteriography in predicting hemodynamically significant stenoses as defined by duplex scanning.