1. The average blood pressure over 24 h and its variability were measured in eight unrestricted subjects before and after commencing therapy with a new β-adrenoreceptor-blocking agent, tolamolol.
2. The drug caused a fall of 15±6 mmHg in mean arterial pressure and heart rate fell by 13 beats/min. The variation in blood pressure and heart rate over 24 h was unchanged after treatment.