In order to study the systemic and coronary haemodynamic effects of felodipine, a new dihydropyridine derivative, 10 patients with coronary artery disease were studied during cardiac catheterization. Measurements were performed at rest and during pacing-induced angina pectoris. At rest, the heart rate rose from 70 +/- 20 to 78 +/- 20 (P less than 0.05), the systemic arterial pressure decreased by about 20% (P less than 0.01) and the cardiac index rose from 2.9 +/- 1.2 to 4.0 +/- 1.0 (P less than 0.05). The coronary sinus flow (CSF) increased about 50% (P less than 0.01). During pacing to the same heart rate as in the control measurements, felodipine induced similar changes in systemic haemodynamic values as in the resting position. Myocardial lactate extraction and ST segment depression were not significantly altered. After felodipine, the pacing rate could be further increased in 7 patients as compared with the control value. Both systemic and coronary effects were then very similar compared with those during the lower pacing rate. In conclusion, felodipine is a very potent systemic and coronary vasodilator with potential value in the treatment of hypertension and cardiac failure. The drug may also be of value in the treatment of ischaemic heart disease, but further studies with titration of optimal doses are needed in that respect.