The effect of beta-adrenorecptor stimulation on the volume of the urinary bladder in 16 neurologically normal humans without symptoms of micturition disturbances was investigated. Terbutaline, a selective beta2-adrenoceptor stimulating agent, was tested in 9 persons and isoprenaline, a general beta-adrenoceptor stimulating agent, was tested in 7 persons. After terbutaline the maximum increase in the bladder volume was 10% and on an average aroung 5%. After isoprenaline the maximum increase in the bladder volume was 15% and on an average around 5%. Terbutaline as well as isoprenaline administration resulted in tachycardia and an increased pulse pressure. The tachycardia was somewhat more marked after isoprenaline. In conclusion, only a small increase in the volume of the urinary bladder was noted after beta-adrenoceptor stimulation in neurologically normal humans without symptoms of micturition disturbances, in contrast to effects achieved in some patients with urgency. Terbutaline seems to have less cardiac effects compared to isoprenaline and is therefore to be preferred when beta-adrenoceptor stimulation is required in patients with urgency.