The assessment of stenotic arteries is an important parameter for the diagnosis of the coronary heart disease and for the indication of a bypass operation. A system has been developed to digitize and process frames from 35 mm- cinecardiographic films on the computer. Vessels filled with contrast medium are recognized automatically by their typical density profiles. The contour finding takes into account the special edge form of the projected boli. When the bolus contours are determined the degree of diameter narrowing can easily be calculated. A further step to evaluate an obstruction is to integrate over the vessel width and to re-transform the mainly exponential imaging process in order to reconstruct the original cross-sectional area of the bolus or its diameters, respectively. In this way even with only one projection a semi-quantitative prediction of an excentricity becomes possible. The correlation of computer measures with known model dimensions and with clinical findings is discussed briefly.