We evaluated 19 female and 18 male patients with bladder exstrophy, who had completed staged reconstruction, had required no further surgery and underwent urodynamic studies. Of the male population 61% were continent based on a significantly higher urethral continence length (25.8 +/- 6.4 mm., mean plus or minus standard error) and a higher urethral closing pressure (69.4 +/- 5.8 cm. water) compared to the incontinent male population (11.4 +/- 3.1 mm. and 43.4 +/- 4.6 cm. water). No significant difference was noted in the bladder capacity of these 2 groups. Of the female population 57.9% were continent. They also demonstrated a higher urethral continence length (21.1 +/- 4.4 mm.) and a higher urethral closing pressure (62.7 +/- 10.2 cm. water) compared to the incontinent female subjects (8.4 +/- 2.5 mm. and 32.7 +/- 6.9 cm. water). Moreover, those who were continent had a significantly higher bladder capacity (201.2 +/- 39.5 ml.) compared to those who were incontinent (84.3 +/- 23.6 ml.). These findings support a multifactorial mechanism in achieving continence but they suggest that of all the factors urethral length may be the most important.