Acute coronary obstruction occurred in two patients during coronary angiography. In one case the obstruction was in the left main coronary artery; in the other it was close to the origin of the left anterior descending artery. In both cases acute cardiac ischaemia ensued, with electromechanical dissociation and collapse, which was not reversible by resuscitation. Rapid disobliteration of the occluded coronary artery was done with a guide-wire pushed through the obstruction via the coronary catheter. The recanalisation was completed by an intracoronary perfusion of streptokinase in one case. In both cases recovery was rapid and spectacular. The occurrence of acute ischaemia during coronary angiography should suggest accidental coronary occlusion. If a thromboembolic origin is suspected, transluminal disobliteration should be attempted. It is simple and can reverse a dangerous condition.