To improve the assessment of the hemodynamic significance of borderline iliac stenoses (stenosis with a peak systolic velocity [PSV] ratio between 1.5 and 3.5) by means of hyperemic duplex scanning. The duplex ultrasound parameter-absolute increase in PSV across the stenosis after exercise (Delta PSV(e))-was studied prospectively.Fifty-eight legs in 53 consecutive patients with symptomatic arterial obstructive disease with borderline iliac stenosis were studied prospectively. Ultrasound velocity data collected after exercise on a bicycle ergometer at 2 W/kg during 2 minutes were judged against the assessment of the hemodynamic significance by means of intraarterial pressure measurement, before and after the administration of 50 mg papaverine.On the basis of receiver operating characteristic curves traced for 43 iliac stenoses in 39 patients who finished the exercise, Delta PSV(e) > or = 1.4 m/s had optimal sensitivity of 93% (95% confidence interval [CI],.77-.99), specificity of 87% (95% CI,.60-.98), positive predictive value of 93% (95% CI,.77-.99) and negative predictive value of 87% (95% CI,.60-.98).The results of this study show that Delta PSV(e) with a cutoff value of 1.4 m/s in combination with the PSV ratio improves the assessment of the hemodynamic significance of borderline iliac artery stenoses if the patient can accomplish the workload.