Transluminal coronary angioplasty can serve as a model for controlled coronary artery occlusion and reperfusion which enables assessment of short-term changes in collateral vessel filling in patients with severe atherosclerotic coronary artery disease. In 16 patients with isolated left anterior descending or right coronary artery disease (greater than or equal to 75% stenosis) and normal left ventricular function, collateral filling to the artery being dilated was visualized by contrast injection into the contralateral artery using a second arterial catheter. During balloon inflation, contralateral dye injection was performed as soon as the patient developed angina or ST-T changes or at 90 seconds in those patients without symptoms or signs of ischemia. Grades of collateral filling from the contralateral vessel were: 0 = none; 1 = filling of side branches of the artery to be dilated via collateral channels without visualization of the epicardial segment; 2 = partial filling of the epicardial segment via collateral channels; 3 = complete filling of the epicardial segment of the artery being dilated via collateral channels. At baseline angiography, nine patients had grade 0 collateral filling, seven had grade 1 and none had grade 2 or 3. During coronary occlusion by balloon inflation, collateral filling improved by one grade in eight patients, two grades in five patients, three grades in two patients and remained the same in one patient.(ABSTRACT TRUNCATED AT 250 WORDS)