In order to investigate the effects of urogenital prolapse on lower urinary tract function, we studied 61 women with stage III to IV pelvic organ prolapse (prolapse group) and 40 volunteers without prolapse (control group). Each woman underwent urinalysis, urinary questionnaire, pelvic examination, and urodynamic study. The incidence of urinary symptoms, including urinary frequency and urgency, stress/urge incontinence, incomplete emptying, difficult voiding and nocturia, were significantly higher in the prolapse group compared to the control group (p < 0.05). Urodynamic parameters, including residual urine, total bladder capacity, and bladder volume at strong desire to void, were not significantly different between the two groups (p > 0.05). Maximal flow rate, bladder compliance at urgency, functional urethral length, and maximal urethral closure pressure, however, were significantly higher in the control group compared to the prolapse group (p < 0.05). In addition, there was a higher incidence of poor pressure transmission ratio in the prolapse group (p < 0.01). The results indicated that severe urogenital prolapse could produce abnormal clinical and urodynamic results.