In a prospective study the effect of Betaloc therapy on pregnancy-associated mild and moderately severe hypertension has been examined. Besides the effects on the mother the changes of foetal heart rate were also observed. The antihypertensive therapy was performed with daily 3 x 100 mg (3 x 1 tab) oral doses of Betaloc in 30 pregnant women with 140-170 mmHg systolic and 90-110 mmHg diastolic blood pressure values at admittance. In the course of the examinations definite and statistically significant fall of systolic flood pressure could be observed following the onset of Betaloc therapy as early as on the first day of drug administration which could be maintained during therapy. Somewhat less definite but the same change was observed in the diastolic blood pressure. Maternal pulse rate was significantly higher before therapy than after finishing Betaloc therapy. Notable foetal bradycardia was not observed, in the course of Betaloc administration the decrease of foetal heart rate did not surpass the normal limit values. During the therapy no side-effect attributable to the drug was observed.