Ischemic heart disease is the most common cause of congestive heart failure, which often begins after acute myocardial infarction. To better delineate the clinical characteristics and outcomes of patients in whom congestive heart failure develops after acute myocardial infarction in the thrombolytic era, we prospectively evaluated patients enrolled in six of the TAMI trials. The study cohort comprised 1619 consecutive patients who had at least 1 mm of ST-segment elevation in two contiguous electrocardiographic leads within 6 hours of the onset of acute myocardial infarction and who received intravenous thrombolytic therapy. We prospectively collected clinical characteristics, baseline demographics, acute and 1-week angiographic variables, and in-hospital and 1-year outcome data. We performed stepwise multivariable regression analysis to determine the noninvasive and invasive predictors of the development of in-hospital congestive heart failure. Congestive heart failure developed in 301 patients in the hospital (19% of 1521 patients admitted were not in heart failure). These patients were likely to be older and female, have diabetes mellitus and previous myocardial infarction, and have an anterior wall myocardial infarction. On acute angiography, they had lower ejection fractions and a higher incidence of multivessel disease. Patency at 90 minutes was lower in the patients with congestive heart failure, and acute mitral regurgitation occurred in 1.6% versus 0.21% of patients without congestive heart failure. Patients with congestive heart failure had higher mortality, more in-hospital complications, and longer hospitalizations. At 1-year follow up, 21% of the patients in whom congestive heart failure developed had died versus 5% in the group without congestive heart failure. Predictors of new congestive heart failure included increased age, anterior wall myocardial infarction, lower pulse pressure and systolic blood pressure, diabetes mellitus, and the presence of rales on admission. The acute angiographic variables of reduced ejection fraction, increased number of diseased vessels, and attempted percutaneous intervention improved the concordance of the predictive model by 6%. Congestive heart failure remains a common clinical problem after acute myocardial infarction and is associated with a twofold increase in in-hospital morbidity and a fourfold increase in in-hospital and 1-year mortality. The development of congestive heart failure in the hospital can be predicted from noninvasive and invasive baseline characteristics. We present a simple table to predict congestive heart failure from baseline characteristics and invasive information.