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 The sphere is inserted into the bladder and withdrawn through the urethra at a steady rate.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 7 mm were performed. The mean urethral resistance as measured by the largest sphere (0.07+/-0.03) was significantly greater than that measured by the medium sphere (0.06+/-0.02, p<0.0001), which was significantly larger than that measured by the smallest sphere (0.04+/-0.01, p<0.0001). 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).