This report describes a method of quantifying the inner volume (lumen volume) of a contrast medium-filled femoral artery from a roentgenogram by computerized image analysis. The various factors influencing the accuracy of the volume determination are analyzed and an image-processing procedure for the elimination of artifacts due to crossing arteries is described and evaluated. The presented methods have been used in a large study of 281 patients and the short-term reproducibility has been found to be 1.00.