Left atrial abnormality on the electrocardiogram (ECG) has been considered an early sign of hypertensive heart disease. In order to determine if echocardiographic left atrial enlargement is an early sign of hypertensive heart disease, we evaluated 10 normal and 14 hypertensive patients undergoing routine diagnostic cardiac catheterization for echocardiographic left atrial enlargement. All patients had normal coronary arteriography, sinus rhythm, normal left ventricular volumes and function, no valvular disease, and no echocardiographic or ECG left ventricular hypertrophy. No patient met ECG criteria for left atrial abnormality. The mean left atrial dimension was 3.46 +/- 0.3 cm in normal individuals versus 4.04 +/- 0.3 cm in the hypertensive patients (p less than 0.01). The left atrial index was also higher in the hypertensive group, 2.18 +/- 0.45 versus 1.88 +/- 0.10 cm/m2 (p less than 0.05), and the left atrial-to-aortic root dimension ratio was significantly higher in the hypertensive group, 1.36 +/- 0.20 versus 1.17 +/- 0.07 (p less than 0.01). We conclude that echocardiographic left atrial enlargement may be an early sign of hypertensive heart disease in patients with no other discernible cause of left atrial enlargement.