I studied 84 pregnant women with mild to moderate essential hypertension, aged 22-40 (average of 29.5 + 5.4 years). After determination of pregnancy the existing hypertensive treatment has been stopped. Blood pressure measurements were performed twice every 3 minutes, with a mercury sphygmomanometer, at least 2 weeks after withdrawing hypertensive treatment, in a sitting position, on a left arm after 1 hour break. Among 84 women, the blood pressure of 36% ranged below 140/90 mm Hg at the end of 1 trimester. At the end of II trimester the percentage reached 54% and during the last trimester of pregnancy it has not changed significantly (52%). In the III trimester about 43% of all studied women showed the tendency of normalizing the blood pressure values to 135/85 mm Hg. Approximately 82% of women did not require pharmacological hypertensive treatment.