The objective of this study was to assess the acute and chronic effects of estradiol on the myocardial performance index (MPI) in hypertensive postmenopausal women. There are conflicting reports on the effects of estrogen on left ventricular function in postmenopausal women, and we are unaware of any study on the myocardial performance index in the postmenopausal state. We undertook a prospective, randomized, double-blind, placebo-controlled study in 34 women, distributed into an estradiol group or a placebo group. After 90 min and at 12 weeks of administration of 1 mg of oral estradiol we evaluated, by Doppler echocardiography, its effects on the MPI. The estradiol group showed no alteration in the MPI after 90 min of the administration of estradiol. On the other hand, after 12 weeks of treatment we observed a statistically significant decrease of isovolumic relaxation time, from 127+/-23 ms to 106+/-16 ms (p < 0.001 and of the MPI from 0.63+/-0.13 to 0.48+/-0.09 (p < 0.01) and an increase in ejection time, from 297+/-32 ms to 330+/-31 ms (p < 0.01). In conclusion, estrogen replacement therapy over a period of 12 weeks showed a significant improvement in the MPI in hypertensive postmenopausal women, whereas the acute administration did not have any effect.