41 female patients with a stress incontinence of grade II or III were treated with 2 mg estriol daily over a period of 2–4 months. The function of the bladder was objectively evaluated by urethrocystotonometry. A significant rise of the urethral pressure profile could be demonstrated in 95% (39/41) of patients. An improvement of the stress incontinence by one clinical grade could be shown, but in no case a completely continent bladder sphincter.