Rest and exercise echocardiography (at dynamic and isometric exercise) were performed in 30 postmenopausal women (aged 54 +/- 4 years) with borderline to mild hypertension. They were then divided into 2 groups: 17 women who started oral hormone replacement therapy (0.625 mg/day conjugated estrogens or 2 mg/day estradiol) and a control group of 13 nonusers. After 6 to 9 months, a second echocardiography was performed in 26 women (4 withdrew). There were only a few changes in values obtained in the 12 controls at the end of follow-up compared with baseline. Primarily, these changes included a slight decrease in systolic blood pressure at rest and on exercise. Several significant morphologic and hemodynamic alterations appeared in 14 hormone users. Left ventricular cavity dimensions and mass became smaller: mean end-diastolic diameter decreased from 45.9 +/- 3 mm at baseline to 44.4 +/- 3 mm at study termination (p = 0.007). The corresponding values for end-systolic diameter were 25.8 +/- 4 mm and 23.9 +/- 4 mm (p = 0.006); for left atrium diameter, it was 34.5 +/- 4 mm and 32.5 +/- 4 mm (p = 0.001); for left ventricular wall width, it was 19.9 +/- 2 mm and 19.3 +/- 2 mm (p = 0.02); for left ventricular mass, it was 197 +/- 28 g and 179 +/- 32 g (p = 0.006). The resting aortic blood flow velocity and acceleration increased: 119 +/- 18 cm/s before therapy versus 129 +/- 23 cm/s while on hormone substitution (p = 0.04), and 13.6 +/- 3 m/s2 versus 16.5 +/- 4 m/s2 (p = 0.008), respectively. Mean rest to peak exercise systolic blood pressure difference became smaller after hormones: 39 +/- 19 mm Hg versus 28 +/- 13 mm Hg (p = 0.03) during dynamic exercise, and 43 +/- 22 mm Hg versus 25 +/- 13 mm Hg (p = 0.004) during isometric exercise. The above data probably indicate that with hormone replacement therapy, there is an improvement in cardiac function both at rest and during exercise.