To study the voiding pattern after a 'normal' vaginal delivery, uroflowmetry and residual urine (RU) measurements (ultrasonography) were performed at the first postpartum voiding and on the 3rd and 5th postpartum days in 51 primiparous women. The bladder volume and the RU were significantly increased, while the corrected (for volume differences) peak flow rate was significantly decreased in the immediate postpartum period. The RU was positively correlated to the total bladder volume (r=28, p=O.05), birthweight (r=0.29, p=0.04) and head circumference (r=0.37, p=0.01), indicating that overdistension of the bladder, possibly due to transiently impaired nervous function, caused by mechanical stress, may play a role. No parturients developed acute urinary retention, and the voiding pattern normalized within a few days. No urinary infections were diagnosed. No correlation could be established between the time from delivery to the first voiding and the voided volume or the total bladder volume, respectively. It is concluded that the emptying function is slightly impaired, which, however, seems to be of limited clinical significance, and that the time after delivery per se is a poor predictor of the bladder volume.