Summary. The acute effects of a single, 20 mg oral dose of nitrendipine were studied in 10 women at between 32 and 42 weeks gestation with stable pregnancy-induced hypertension (PIH). Blood pressure (BP), maternal heart rate and fetal heart rate (FHR) were assessed for 8 h after nitrendipine intake together with the plasma levels of nitrendipine, noradrenaline, adrenaline, plasma renin activity (PRA) and vasopressin. The mean initial systolic/diastolic BP was 158 (SEM 3.7)/ 108 (SEM 2.7) mmHg. Within 1 h stable, reduced mean BP-levels of 141–145/90–95 mmHg were reached and maintained for 4 h after medication. This antihypertensive effect was closely related to the maternal plasma concentration of nitrendipine, which reached a maximum of 9.1 (SEM 2.6) ng/ml 3 h after tablet intake. After 4 h, systolic and diastolic BPs slowly increased in parallel to a successive decrease in plasma concentrations of nitrendipine. Maternal heart rate increased by less than 10%, while FHR remained unchanged. No hypotensive incidents occurred. The initial mean plasma concentrations of noradrenaline, adrenaline, vasopressin and PRA did not change during the treatment. No major maternal and no fetal side-effects were observed. Three of 10 patients experienced mild, transient facial flushing.