A procedure for quantitative evaluation of coronary stenosis is presented. Coronary artery contour detection is based on Ist and 2nd derivative computation and densitometric analysis. The procedure is a necessary tool for the evaluation of the effect of a pharmacological treatment or the performance of interventional techniques. Validation of the procedure has been performed by using a physical phantom with different calibers and a variability study based on a set of 12 coronary angiograms.