Two studies of the pharmacokinetics and pharmacodynamics of intravenous nifedipine infusion were performed: the first, a randomised double-blind crossover study of nifedipine and its vehicle in eight subjects, the second a dose ranging study in nine subjects. Nifedipine pharmacokinetics did not vary with dose or duration of infusion up to 8 h, and are similar to those reported for other nifedipine preparations. Nifedipine increased heart rate and forearm blood flow and decreased blood pressure after bolus injection but not during prolonged infusion. The vehicle decreased blood pressure and increased forearm blood flow after bolus injection but not during prolonged infusion. It did not affect heart rate. The vehicle's haemodynamic activity has not been previously recognised and is of potential importance in the study of this and similar preparations of calcium antagonists.