Anamnestic findings and urodynamic parameters of 377 patients suffering from urinary stress incontinence were evaluated before and one year after several incontinence operations (anterior colporrhaphy, colposuspension according to a modified Marshall-Marchetti-Krantz procedure and vesico-urethral suspension according to Pereyra). Two groups were formed: group I including 246 women who experienced successful operation and group II consisting of 131 patients suffering from recurrent stress incontinence. Mean age, -parity and -body-weight did not influence the result of surgical treatment. However, there was a statistical significant difference between both groups concerning the functional urethral length (alpha U-test = 0.00118) and the maximum urethral closure pressure (alpha much less than 0.001). By the addition of the preoperatively measured functional urethral length and the maximum urethral closure pressure a new parameter was determined by which group I and group II could be separated clearly. The difference was statistical significant (alpha much less than 0.001). According to these data the risk of recurrence could be evaluated preoperatively: the cure rate below the 25th percentile (0-56) of this new parameter was 49%, in between the 25th and the 50th percentile (57-70) the cure rate was 60%, in between the 50th and 75th percentile (71-84) 75% and above the 75th percentile (x greater than 84) 79%. Our data show clearly that the addition of the function urethral length and the maximum urethral closure pressure is an useful parameter to calculate the risk of recurrence of stress incontinence even prior to its surgical treatment.