To study subjective and objective changes of micturition after colposuspension, 80 patients were evaluated before and after surgery. It was found that colposuspension may introduce an element of urethral obstruction, which leads to a significant proportion of immediate as well as late voiding difficulties. Thus, 25% of the patients developed severe voiding difficulties in the immediate postoperative course. Low pressure voiding (Pdetless than 15 cm water) preoperatively was found to predispose significantly to immediate postoperative voiding difficulties. Another 20% developed late voiding difficulties. Increased urethral resistance preoperatively was found to predispose significantly to late postoperative voiding difficulties. Increased urethral rigidity is suggested as an underlying factor. Only four (5%) of the patients developed both immediate and late postoperative voiding difficulties. The detrusor pressure at maximum flow was found to be an unreliable parameter in assessing the true potential of the detrusor. It is emphasized that a thorough preoperative evaluation of both bladder and urethral function and the use of a proper surgical technique are required to avoid voiding difficulties after colposuspension.