In recent years there has been an increasing interest in quantitative analysis of coronary cineangiograms and already for a longer time of left ventricular cin­ eangiograms. The needfor quantitationofcoronary arterialdimensions has been stimulated by the introduction ofnew therapeutic procedures in the catheteriza­ tionlaboratory, suchas the balloon dilatationtechnique (PTCA) and thromboly­ tic therapy, by the need to study the vasoactive responses of pharmaceutical agents, and also by the desire to study the progressive nature ofcoronary artery disease with the ultimate goal to find ways to bring a halt to the progression of coronary atherosclerosis or even achieve regression of the disease. Parallel with these clinical developments, rapid