OBJECTIVE The purpose of this study was to determine the simplicity, safety, anatomic, and functional success of using the uterosacral ligaments for correction of significant complex uterine and vaginal vault prolapse by the vaginal route. METHODS Fifty women with uterine or vaginal vault prolapse with descent of the cervix or the vaginal vault to the introitus or greater were treated between 1993 and 1996 by the same surgeon with bilateral uterosacral ligament fixation to the vaginal cuff by the vaginal route. Included were patients with significant enterocele, cystourethrocele, rectocele, and stress urinary incontinence who had concomitant repair of coexisting pelvic support defects. An etiology of vaginal vault prolapse is discussed. RESULTS Uterosacral ligaments were identified and used for successful vaginal vault suspension by the vaginal route in all 50 consecutive patients without subsequent failure or significant complications with a maximum follow-up of 4 years. One patient had recurrent stress urinary incontinence and two had asymptomatic cystoceles. Three patients had erosion of monofilament sutures at the vaginal apex. CONCLUSIONS In these 50 patients with significant complex uterine or vaginal vault prolapse, uterosacral ligaments could always be identified and safely used for vaginal vault suspension by the vaginal route with no persistence or recurrence of vaginal vault prolapse 6 to 48 months after surgery. Excessive tension by the surgeon on tagged uterosacral ligaments at the time of hysterectomy may be an etiologic factor in vaginal vault prolapse.