Sixteen healthy women, and 13 with stress incontinence were investigated by simultaneous urethrocystometry during the initiation of voiding. In the healthy women, there was a decrease in the maximum intra-urethral pressure immediately before micturition. A few seconds later (mean 3.0 sec), the intravesical pressure increased. As a result, the urethral closure pressure decreased to zero, and urine started to escape from the urethra. In the patients with stress in continence, three different ways of initiating micturition were observed. Five patients initiated voiding by the Valsalva manoeuvre, 3 mainly by decreasing the maximum urthral pressure, and 5 mainly in the same way as the healthy women. The results suggest that preoperative analysis of the micturition pattern by means of simultaneous urethrocystometry can be of value for the choice of operative procedure, and thereby make it possible to avoid or reduce postoperative retention of urine.