The use of electrocardiography in sports or military screening is considered an effective tool for diagnosing potentially fatal conditions. The present study was designed to compare the yield of electrocardiographic criteria for left ventricular hypertrophy (LVH) criteria for the diagnosis of LVH and hypertrophic obstructive cardiomyopathy in subjects aged <20 years and >30 years. The association between the electrocardiographic (ECG) criteria for LVH (ECG-LVH) and echocardiographic findings was compared in 4 groups of air force academy candidates: (1) young candidates undergoing echocardiography because of ECG-LVH findings (n = 666); (2) young candidates without ECG-LVH findings undergoing routine echocardiography (n = 4,043); (3) older designated aviators undergoing echocardiography because of ECG-LVH findings (n = 196); and (4) older designated aviators undergoing routine echocardiography without ECG-LVH findings (n = 1,098). The predictive value of ECG-LVH findings for echocardiographic LVH, left ventricular mass, posterior wall thickness, and interventricular septal thickness were compared among the 4 groups. The ECG criteria in young subjects correlated with the left ventricular mass and posterior wall thickness but not with the interventricular septal thickness. In older subjects, these criteria correlated with left ventricular mass, interventricular septal, and posterior wall thickness. The positive and negative predictive value of ECG-LVH findings for the echocardiographic diagnosis of LVH in young subjects was 6.0% and 99.0%, respectively. In older subjects the positive and negative predictive value of ECG-LVH findings was 34% and 93%, respectively. In conclusion, ECG criteria are probably a useful tool for exclusion of LVH in young and older subjects; however, their low positive predictive value would probably lead to unnecessary echocardiographic tests, particularly in young subjects.