Bisoprolol is a new highly beta 1-selective beta-adrenoceptor blocking drug; it is devoid of intrinsic sympathomimetic effects. Its haemodynamic effects are those expected from beta 1-blockade, heart rate is reduced at rest and on exercise, cardiac output falls and peripherial resistance is increased. Consequent on the beta 1-selectivity there is much greater inhibition of exercise tachycardia compared to inhibition of isoprenaline-induced falls of diastolic blood pressure, in contrast to propranolol. Studies in asthmatics confirm the selectivity of bisoprolol. Bisoprolol has similar solubility in water and organic solvents and predictably therefore about half is excreted by the kidneys unchanged, half metabolized by the liver. Estimates of half-life average about 10-12 h, this is in accord with the therapeutic efficacy of once daily administration. Therapeutic studies have demonstrated the efficacy of bisoprolol in angina pectoris, arrhythmias and hypertension. Comparative studies against atenolol and verapamil in angina suggest similar efficacy. In hypertension a similar antihypertensive effect to nifedipine has been found, while a significantly greater lowering of blood pressure was seen than that obtained with a diuretic. Some studies have also suggested more consistent antihypertensive effect from bisoprolol than atenolol 24 h after administration. This may have been a dosage phenomenon or reflects the longer plasma elimination half-life of bisoprolol, and requires confirmation. Bisoprolol has a favourable side-effect profile.