The effect of a pre-operative dose of metoprolol on the catecholamine and cardiovascular responses to tracheal intubation and surgery, cardiac complications and intra-operative blood loss, were studied in patients undergoing elective hysterectomy during general anaesthesia. The study was double-blind and placebo controlled. The patients received metoprolol 100 mg or placebo orally 1-25 h before anaesthesia. In patients given metoprolol, heart rate and mean arterial pressure were lower during the first 45 min of anaesthesia. Plasma adrenaline and noradrenaline concentrations increased in both groups in response to tracheal intubation and surgery, but were higher after metoprolol. The incidence of arrhythmias was less after metoprolol. The mean operative blood loss was greater in the placebo group (486 +/- 170 ml (SEM) compared to 231 +/- 43 ml (SEM) after metoprolol). We conclude that oral premedication with metoprolol attenuates the hypertensive response to tracheal intubation and reduces both arrhythmias and operative blood loss.