A novel coronary dilation method is disclosed wherein a guiding catheter having at least one side arm is continuously flushed with heparinized saline during the dilation process except for momentary interruptions for recording coronary pressures. In accordance with the preferred embodiment method, a dilating catheter (of a balloon-type) is inserted with the guiding catheter and is also continuously flushed through an inner lumen except for periodic pauses to record coronary pressures. A stylet having a thickness substantially thinner than the inner lumen of the dilating catheter is inserted therein, which stylet terminates 3 to 5 mm. short of the end of the catheter. The outer lumen of the dilating catheter is utilized to inject dye and saline for inflating the balloon to perform the coronary dilation. Using the method of the present invention, the patient need not be entirely heparinized nor will significant difficulties be encountered in directing the dilating catheter to the obstruction to be dilated.