This paper is concerned with a method to detect left ventricular boundaries and the subsequent volume computation from a cineangiogram by a digital computer. It will first describe three digital techniques: (1) to restore the original dimensions by a logarithmic transformation; (2) to reduce noise by averaging images; and (3) to subtract images after and before dye injection, and then a boundary detection method based on statistical principles and heuristics. A method to locate the aortic valve will also be described. Experimental results on several cine frames will be presented to demonstrate the feasibility of these techniques. Once the boundary of the ventricle is determined, the computation of the volume is performed by the usual Simpson's rule. © 1973.