An Otis urethrotome has been modified to permit passage into the kidney over an 0.038-inch guidewire by drilling a 3/16-inch hole through the tip. I have used this instrument to aid in the performance of 36 nephrostomy tract dilations without significant complications. When compared with 20 Amplatz tract nephrostomy dilations, the new method was quicker, requiring 4.3 minutes versus 6.5 minutes. This instrument is especially useful for tracts where significant renal fascial scarring makes Amplatz dilation difficult. Ease of tract dilation, as well as decreased time to dilate, make this technique a useful addition to standard nephrostomy tract dilation techniques.