The antihypertensive efficacy of a new beta-blocker, celiprolol, was compared with that of a well established antihypertensive drug, metoprolol. Systemic and forearm haemodynamic effects were investigated using echocardiography and two-dimensional pulsed Doppler flowmetry, respectively. Twenty hypertensive patients completed the double-blind crossover randomized study. Each 6-week active treatment period was both preceded and followed by 2 weeks of placebo treatment such that the total duration of the study was 18 weeks. Despite comparable efficacy in reducing systolic and diastolic blood pressures by approximately 10% of the basal value, the two drugs differed in their systemic and haemodynamic effects. Celiprolol significantly decreased forearm peripheral resistance and total peripheral resistance. Cardiac output remained unchanged and forearm blood flow was increased. Metoprolol reduced cardiac output through a reduction in heart rate, but stroke volume was unaltered. Neither drug significantly modified cardiac performance, as evaluated by left ventricular circumferential fibre shortening and left ventricular ejection fraction. Differences in the systemic and regional haemodynamic effects of the two drugs could account for the different blood pressure response seen in some patients. There was no observable change in left ventricular wall thickness or left ventricular mass. These results confirm previous reports which demonstrate that antihypertensive treatment with beta-blockers does not reduce left ventricular mass in patients with a left ventricle of normal size. It is generally accepted, however, that the ability of beta-blockers to reverse left ventricular hypertrophy is unrelated to the individual pharmacological characteristics of each agent.