Urethral pressure profile measurement is a well established method in clinical investigations of urethral function. Several types of constant flow catheters have been used. Flow systems give accurate results only within certain limits. The profile depends on catheter size, flow rate, withdrawal rate and size of the infusion holes. A comparison between open systems of different design might therefore be difficult. In this study, an open-flow system is compared to two types of microtip transducer catheters (Millar; Gaeltec). The microtip transducer catheters are not limited by the parameters which can give measurement artifacts in an open-flow system. They are also accurately comparable, easy to handle and can be used in different body positions.