The anamnestic, clinical and urodynamic findings of 377 consecutively investigated women were evaluated. 86 (23%) patients showed bladder instability. The intensity of involuntary bladder contractions and the occurrence of incontinence in association with involuntary detrusor contractions influenced the clinical significance of unstable bladders. The maximum urethral closure pressure however had no influence on it. Urge incontinence was the most reliable symptom distinguishing those patients with bladder instability. Frequency of micturition, nocturia and nocturnal enuresis were less reliable in this respect. Urinary tract infections showed no correlation to bladder instability.