The authors report the results of 8 cases of percutaneous transluminal coronary angioplasty of occluded arteries: the artery concerned was the proximal segment of the left anterior descending artery in 5 cases and the proximal segment of the right coronary artery in 3 cases. All patients had unstable angina with a very positive exercise stress test. The conservation of viable myocardium was the result of an excellent collateral circulation from the controlateral vessel in all patients. In 7 out of the 8 cases, the guide wire and dilating balloon were correctly positioned by opacifying the distal segments of the occluded artery by injection of contrast into the controlateral artery. Almost simultaneous injection of the occluded and controlateral vessels allowed evaluation of the length of the occlusion. Controlateral opacification disappeared immediately after adequate recanalisation to reappear during inflation of the balloon. These cases show that in patients with chronic coronary occlusion, opacification of its distal segments by injection of contrast into the controlateral vessel seems to be helpful and without risk to the patient.