It is accepted that pelvic organ prolapse impairs voiding, in particular as regards the anterior vaginal wall. The influence of central and posterior prolapse is more controversial. Mechanical effects, i.e. urethral distortion and compression, have been advanced as causative mechanisms. This study attempts to further elucidate the effect of prolapse on voiding. We investigated 228 patients with symptoms of lower urinary tract dysfunction and/or prolapse using independent flowmetry, clinical and ICS prolapse assessment and translabial ultrasound. As expected, age ( P<0.001), previous hysterectomy ( P = 0.002) and/or incontinence surgery ( P<0.001) negatively influenced flow. As regards prolapse, only enterocele had a consistently negative effect on flow ( P<0.001 for clinical staging, P = 0.002 for ICS assessment, P = 0.005 for ultrasound imaging). The relationship between anterior vaginal wall prolapse and voiding was complex: funneling and opening of the retrovesical angle on ultrasound was associated with improved voiding ( P<0.001), but a cystocele with intact retrovesical angle had the opposite effect ( P<0.001).