OBJECTIVES: This study examined the influence of left ventricular hypertrophy on the accuracy of exercise electrocardiography and echocardiography for detection of coronary artery disease. BACKGROUND: Electrocardiographic repolarization abnormalities caused by left ventricular hypertrophy compromise the diagnostic accuracy of exercise electrocardiography but not of exercise echocardiography. The relative merits of these investigations are less well defined in patients with hypertrophy but without electrocardiographic (ECG) changes. METHODS: We prospectively evaluated 147 consecutive patients without prior myocardial infarction undergoing both exercise echocardiography and coronary arteriography. Coronary stenoses > 50% diameter were present in 62 patients (42%). Positive test results were defined by a new or worsening wall motion abnormality or > 0.1 mV of ST depression. Echocardiographic left ventricular hypertrophy (mass > 131 g/m2 in men, > 100 g/m2 in women) was identified in 68 patients. A subgroup with clinically suspected hypertrophy was defined according to the presence of ECG evidence of hypertrophy, hypertension or aortic stenosis. RESULTS: The overall sensitivity of exercise echocardiography exceeded that of exercise electrocardiography (71% vs. 54%, p = 0.06). Echocardiographic hypertrophy had no significant effect on the sensitivity of either test. The specificity of exercise echocardiography exceeded that of exercise electrocardiography (91 vs. 74%, p = 0.01). In patients with hypertrophy, the specificity of exercise echocardiography exceeded that of exercise electrocardiography (95% vs. 69%, p < 0.01), whereas among patients without hypertrophy, the specificities (respectively, 87% and 78%) were more comparable. The accuracy of exercise echocardiography exceeded that of the exercise ECG in the overall group (82% vs. 65%, p = 0.002) and in patients with hypertrophy (85% vs. 60%, p = 0.004), but this difference was less prominent in patients without hypertrophy (80% vs. 69%, p = NS). In patients with clinically suspected hypertrophy, exercise echocardiography demonstrated a higher sensitivity, specificity and accuracy than exercise electrocardiography. The cost incurred in the identification of coronary disease was least with a strategy involving use of the exercise echocardiogram instead of routine exercise testing in patients with known or clinically suspected left ventricular hypertrophy. CONCLUSIONS: Exercise echocardiography is more accurate than exercise electrocardiography for the detection of coronary artery disease in patients with known or clinically suspected left ventricular hypertrophy.