The aim of this study was to evaluate a new method to measure urethral resistance among 66 women with urinary incontinence. A stainless steel sphere attached to a guide wire was developed. The sphere is inserted into the bladder and withdrawn through the urethra at a steady rate. Serial measurements with spheres of 5, 6 and 7mm were performed. The mean urethral resistance as measured by the largest sphere (0.070.03) was significantly greater than that measured by the medium sphere (0.060.02, p0.0001), which was significantly larger than that measured by the smallest sphere (0.040.01, p0.0001). There was good correlation of urethral resistance with maximum urethral closure pressure (MUCP) by this technique, but no correlation with Valsalva leak point pressure (VLPP).