The ideal antihypertensive agent for lowering very high blood pressure levels rapidly in severe hypertension of pregnancy still eludes researchers. This pilot study was conducted to determine the appropriate dosage regimen for isradipine in black patients with severe hypertensive disorders of pregnancy. Ten black patients with gestational age > or = 30 (range 30-38) weeks and diastolic blood pressure (DBP) > or = 110 (range 110-148) mmHg following 2 h of bed rest were recruited following informed consent. None of the patients had symptoms or signs of hypertensive crisis. After correction of hypovolaemia (using central venous pressure monitoring) with Ringer's lactate, high blood pressure was lowered by an isradipine infusion. Fetal heart rate was continuously recorded using a cardiotocograph. All blood pressure measurements were made using the same mercury sphygmomanometer by a single observer. The infusion rate of isradipine was adjusted at regular intervals until blood pressure control (DBP < 95 mmHg) was achieved. The optimal dosage regimen in black patients was found to be an initial dose of 0.15 microgram kg-1 min-1 with increments of 0.0025 micrograms kg-1 min-1 every 15 min until blood pressure control is achieved. Thereafter, a maintenance infusion of 0.15 microgram kg-1 min-1 can be initiated. This dosage regimen is associated with neither maternal hypotension nor fetal heart rate deceleration.