Left ventricular hypertrophy (LVH) portends a worse outcome after non–ST-elevation acute myocardial infarction (NSTEMI). However, its definition has varied and the incremental prognostic information provided by echocardiography has been unclear. Different electrocardiographic and echocardiographic criteria for LVH were compared for their ability to predict in-hospital complications in 451 consecutive patients with a first NSTEMI, 337 of whom had a reliable echocardiogram. Five to 8% had LVH using Sokolow-Lyon or Cornell (voltage or product) criteria on admission; 15%, using either electrocardiographic criteria; and 24%, using echocardiography. LVH predicted the occurrence of adverse events (death, reinfarction, or severe angina or heart failure), with the strongest association found for the Cornell product (50.0% vs 24.9% of patients meeting or not meeting this criterion had complications, respectively; p = 0.002). This association persisted after adjusting for baseline clinical predictors (odds ratio 2.52, 95% confidence interval 1.19 to 5.35), and considering echocardiographic LVH did not improve the prediction. LVH was more closely related to heart failure occurrence than to recurrent ischemic events. A progressive increase in the rate of complications was observed across quartiles of the components of all LVH criteria (17.1%, 23.7%, 31.7%, and 36.2% for Cornell product, respectively; p <0.001). In conclusion, LVH, especially an abnormal Cornell product, increased the risk of heart failure, but was weakly related to recurrent ischemia in patients with NSTEMI. Echocardiographic LVH did not appear to add prognostic information to the electrocardiogram. However, considering LVH criteria in a more quantitative manner may augment their ability to predict adverse events in this population.