The acute effects of oral administration of felodipine 10 mg and nifedipine 10 mg on heart rate, blood pressure, forearm blood flow and hepatic blood flow were studied in nine healthy men. Both drugs caused an increase in heart rate of 16 and 7 beats.min-1, respectively. Hepatic blood flow was significantly increased by 1.2 and 0.41.min-1 after felodipine and nifedipine. There was also a decrease in diastolic blood pressure, 10 and 5 mm Hg, respectively, after felodipine and nifedipine. The forearm blood flow was increased by about 30 ml.100 ml-1.min-1 after felodipine, but nifedipine had no effect. The haemodynamic effects were most pronounced 50 min after drug administration.