Urinary stress incontinence associated with poor urethral sphincter function and indicated by a urethral pressure of less than 10 cm. water was treated in 52 cases with a pubovaginal autogenous fascial sling. No urethral sphincter function could be measured in 7 patients. Of these 52 patients 42 had undergone a previous operation for stress incontinence. The uninhibited detrusor dysfunction that accompanied the stress incontinence in 29 cases ceased after operation in 20 but persisted in 9. Postoperative urethral pressure measurements indicated that while the sling increased urethral pressure it did not cause an obstruction during voiding, since there was a measurable decrease in urethral pressure during a detrusor contraction. Urodynamic determination were useful in patient selection, in the adjustment of sling tension at operation and in the assessment of reasons for failure. A satisfactory result with good urinary control was obtained in 50 cases and the procedure was a failure in 2.