The interaction of a new slow-calcium blocker (nisoldipine) and the beta-blocker metoprolol was evaluated in 16 patients with stable angina. Haemodynamic parameters were determined in a control rest and exercise period. Patients were then randomised equally to nisoldipine (4–8 μg/kg) or metoprolol (10 mg) and the haemodynamics of monotherapy assessed; finally the second drug was administered and the effects of combination determined. At rest nisoldipine reduced systemic blood pressure and vascular resistance ( P < 0.01); heart rate, cardiac and stroke volume indices increased ( P < 0.01) at an unchanged pulmonary artery occluded pressure. Metoprolol alone reduced heart rate ( P < 0.05) and increased the pulmonary artery occluded pressure ( P < 0.05). Combination therapy reduced systemic blood pressure and vascular resistance ( P < 0.01); cardiac index and pulmonary artery occluded pressure increased ( P < 0.01) at an unchanged heart rate. The effect of combination was influenced by the order of administration; an improvement in cardiac performance was particularly evident when nisoldipine was added to metoprolol. The interaction during dynamic exercise was similar to that at rest. Thus these data indicated the haemodynamic safety of concurrent nisoldipine/metoprolol therapy; the addition of nisoldipine to metoprolol appeared to offset in part the cardiodepressant properties of beta-blockade.