Patients with carotid atherosclerosis have an increased risk of coronary events and an increased prevalence of echocardiographic left ventricular hypertrophy. However, little is known regarding the association between electrocardiographic abnormalities and carotid atherosclerosis. The relationship of electrocardiographic evidence of myocardial ischemia and left ventricular hypertrophy to the presence of carotid atherosclerosis was prospectively studied in 349 asymptomatic subjects who underwent echocardiography and carotid ultrasonography. Myocardial ischemia on the electrocardiogram was defined by the presence of localized T-wave inversions, and electrocardiographic hypertrophy was defined by the product of Cornell voltage and QRS duration. Carotid atherosclerosis was present in 21% (72/349) of subjects and was associated with older age, higher systolic and pulse pressures, and greater left ventricular mass. Both ischemia and hypertrophy on the electrocardiogram were strongly associated with carotid plaque. Carotid atherosclerosis was more than three times more prevalent in subjects with electrocardiographic ischemia (69% [11/16] versus 18% [61/333], P < .0001) or electrocardiographic left ventricular hypertrophy (78% [7/9] versus 19% [65/340], P = .0003) than in subjects without these findings. Logistic regression analysis, including standard risk factors, revealed that both ischemia and hypertrophy on the electrocardiogram remained significant independent predictors of the presence of carotid atherosclerosis, along with age and echocardiographic left ventricular mass. These findings suggest that the associations of ischemia and left ventricular hypertrophy with carotid atherosclerosis may contribute to the increased incidence of coronary events in patients with carotid atherosclerosis. (Hypertension. 1996;28:3-7.)