Background: There are few data comparing clinical outcome and potential indications for routine post-myocardial infarction cardiac catheterization and revascularization of patients who sustain a non-Q-wave versus Q-wave infarct after thrombolytic therapy. Methods and Results: A secondary analysis of 2634 patients enrolled in the TIMI II trial with a first myocardial infarction was performed to determine 6-week and 1-year cardiac event rates and identify clinical and angiographic differences between the 1867 patients (70.9%) who evolved a Q-wave infarct and the 767 patients (29.1%) who sustained a non-Q-wave infarct after treatment with intravenous thrombolytic therapy. Male sex (85.3% versus 75.6%; P<.001) and anterior wall infarcts (53.8% versus 43.7%; P<.001) were more frequent in the Q-wave versus the non- Q-wave group. During recombinant tissue-type plasminogen activator (rTPA) infusion, a greater percentage of non-Q-wave patients (37.3% versus 23.5%; P=.001) had normalization of initial ST-segment elevation. Infarct-related artery patency (TIMI flow grade 2 or 3) (P=.02), complete infarct-related artery reperfusion (TIMI 3 flow grade) (P<.001), and the percentage of patients with apredischarge resting left ventricular ejection fraction >55% (P<.001) were greater in the non-Q-wave group. New congestive heart failure during hospitalization developed more frequently in Q-wave patients (18.9% versus 11.6%; P<.001). After 42 days, the occurrences of reinfarction (P=.76), death (P=.76), and combined death or reinfarction (P=.43) were similar in patients assigned to the invasive or conservative postlytic management strategy, regardless of infarct type. One-year mortality was 3.4% versus 4.4% for non-Q-wave versus Q-wave infarct type, respectively (P=.25). Conclusions: Angiographic and clinical differences were observed between patients who present with initial ST-segment elevation and evolve early non- Q-wave versus Q-wave myocardial infarcts after treatment with rTPA, heparin, and aspirin. Early mortality and adverse clinical cardiac events in these patients are not significantly different after a conservative compared with an invasive treatment strategy, regardless of whether the infarct type is non-Q wave or Q wave.