Simultaneous registration of urethral pressure profile and pull-through force was performed to study the dynamics of sphincteric function in 25 female patients. Three separate types of catheters of six different sizes were used. A 6-French smooth catheter was used to measure maximal urethral closure pressure, functional profile length and length to maximal urethral pressure. The results were divided into three groups (A, B and C) with significantly different closure pressure values, only correlated to the age of the patient. In all three groups (A, B and C), the mean maximal urethral closure pressure increased in linear correlation to the catheter diameter and did not bear any relation to the shape of the catheter tip, either of the bulb or the ball type. A significant exponential correlation was demonstrated between pull-through force and catheter diameter. Also the correlation between force and length of the pull-through force curve was exponential, while only the mean values of closure pressure and force correlated exponentially. No further correlations were found, even after force values were ranked to form three other groups (I, II and III). In contrast to the groups A, B and C, no distinct differences in clinical diagnosis was noticed between groups I, II and III. The pressure and force curves can be explained on a physical basis, despite the variety in pathology. On the basis of this evidence it appears that a more accurate measurement of sphincter function in the female can be obtained by measuring pressure and force simultaneously with different sizes of catheters, especially with a diameter of 15 French or more.