The empty (near-empty) bladder can have a volume ranging from 0 to 30 ml. Its diagnosis is effectively and least invasively made by ultrasound (transvaginal superior). It is a key marker of normal bladder function. It is necessary for the accurate assessment of uterovaginal prolapse, as increasing bladder volume has been shown to reduce the extent of the prolapse. Any negative effect of prolapse on voiding is reduced at high bladder volumes compared to voiding from low bladder volumes (due to the same reduction in the extent of the prolapse). An empty bladder is optimal for bimanual pelvic examination and most transvaginal ultrasound examinations including that for uterine version. The retroverted uterus is proving to be of increasing relevance to prolapse. The woman whose bladder is empty post-voiding is at a significantly lower risk of recurrent urinary tract infections. The bladder that can't be emptied is a marker of bladder dysfunction, requiring a fuller investigation. From a surgical point of view, the empty bladder improves access and reduces surgical risks with laparotomy, as well as both laparoscopic and vaginal surgery.