To determine the risk of arterial reocclusion or recurrent ischemia after acute intervention in myocardial infarction, we analyzed the results of coronary arteriography performed acutely and at 1 week in 50 consecutive patients who received acute intervention. Successful recanalization of the infarct vessel was achieved in 46 (92%) patients after therapy with intravenous tissue plasminogen activator, percutaneous coronary angioplasty, or both. Follow-up angiography in 44 showed early reocclusion in 10 patients (23%). Intermittent patency during acute arteriography was always associated with reocclusion; suboptimal (Thrombolysis in Myocardial Infarction [TIMI] class 2) flow was associated with a 50% rate of reocclusion. Although residual stenosis of greater than 50% alone was not predictive of rethrombosis, 90% of all reocclusions were associated with either stenosis greater than 50%, TIMI 2 flow, or intermittent patency. Absence of these angiographic risk factors predicted a 95% patency rate at follow-up. In-hospital cardiac complications occurred in 17 of 23 (74%) patients with residual stenosis of greater than 50% (death in four, ischemia in 13), and late revascularization was required in 53% of survivors. Only 15% of the group with less than 50% stenosis had an in-hospital ischemic event (p less than 0.001). Thus, after acute intervention, an infarct vessel with intermittent patency or suboptimal flow is associated with a high rate of reocclusion. Residual stenosis greater than or equal to 50% appears to predict a high incidence of negative in-hospital clinical outcomes and the need for subsequent revascularization.