The presence of intracoronary thrombus after percutaneous coronary intervention (PCI) worsens clinical outcomes. We performed this study to assess the incidence of intracoronary thrombus after primary angioplasty for acute myocardial infarction (AMI) and the clinical impact of nonocclusive thrombus. In 2,148 patients enrolled in the Primary Angioplasty in Myocardial Infarction (PAMI)-2, Stent PAMI, and PAMI No-Surgery-On-Site trials, we compared clinical and angiographic characteristics of 131 patients (6%) who had angiographically visible thrombus after PCI with those who did not (n = 2,017). In the subset of 2,115 patients with post-PCI Thrombolysis In Myocardial Infarction (TIMI) 2 or 3 flow, we assessed the impact of post-PCI thrombus (n = 110) on in-hospital, 1-month, and 1-year outcomes (reinfarction, ischemic target vessel revascularization [I-TVR], death, and major adverse cardiovascular events [MACEs] [i.e., death, reinfarction, or I-TVR]). Lack of stent use, presence of thrombus before PCI, and no history of PCI were independent correlates of post-PCI thrombus. Patients with nonocclusive thrombus after PCI had more reinfarctions during the index hospitalization (5.5% vs 2.0%, p = 0.03) and at 1 month (6.8% vs 2.3%, p = 0.01) and had nonsignificantly higher I-TVR (during hospitalization 5.5% vs 2.8%, p = 0.13; at 1 month 5.9% vs 3.4%, p = 0.17), but similar mortality and MACE rates as those without post-PCI thrombus. In multivariate analysis, post-PCI thrombus was not a significant predictor of in-hospital or 1-month reinfarction. At 1 year, clinical outcomes were similar between patient groups (reinfarction 8.3% vs 4.7%, p = 0.14; I-TVR 12.5% vs 12.1%, p = 0.91; death 5.9% vs 5.0%, p = 0.68; and MACEs 21% vs 18%, p = 0.54). We conclude that residual intracoronary thrombus after primary angioplasty is relatively uncommon. In patients who achieve TIMI 2 or 3 flow after PCI, intracoronary thrombus is associated with worse cardiovascular outcomes. However, differences in outcomes between patients with and without residual thombus are related to baseline clinical differences rather than thrombus per se.