An infundibular stenosis is defined by a dilated calyx draining through a narrowed infundibulum into a nondistended renal pelvis. We describe the use of ureteroscopy and the holmium:yttrium-aluminum-garnet (YAG) laser to successfully treat an infundibular stenosis in a 27-year-old woman who presented with left flank pain. The holmium:YAG laser is well suited for this application. It can be applied with precise control of the direction and depth of the cut. The retrograde approach avoids the morbidity of a percutaneous nephrostomy and is well suited for treating an anterior infundibular stenosis.