Recanalization of an occluded aortocoronary vein bypass was achieved in six out of seven patients (aged 57 +/- 4 years) 3-40 months after operation and 2-16 weeks after occlusion. The recanalization was done with a specially modified catheter introduced into the stump of the occluded vessel: urokinase was infused followed by balloon dilatation. Subsequent treatment included administration of nitrates, calcium antagonists, aspirin and heparin for at least three months. Repeat coronary angiography after 3-6 months (mean 4.3 +/- 1.0 months) demonstrated vessel patency in four of the six bypasses. One of them, severely stenosed, was again successfully dilated. It is concluded that bypass recanalization can be attempted if the occlusion occurred only a few weeks previously, angiography demonstrates a bypass stump and the state of the peripheral coronary artery makes good outflow likely.