A method for measuring regional variation in coronary blood flow has been developed using image processing techniques applied to sequences of digital coronary angiograms. A series of digital subtraction angiography images is used as a basic data set to form parametric images of blood volume and of contrast arrival time under varying conditions of blood flow. A model relating the image-derived parameters and physiological flow has been developed and validated in animal experiments. The use of rapid image processing methods permits the formation of flow parameter images in a short time, making the method suitable for online assessment of interventional procedures.