50 cases of flexible instrumentation of the intrarenal collecting system are reviewed. 28 were performed by retrograde flexible ureterorenoscopy. The introduction was carried out by combining hydraulic dilation, rigid ureterorenoscopy and a working sheath. 22 cases were performed through a percutaneous route. The indications were both diagnostic (filling defects and/or hematuria) and therapeutic (caliceal stone and/or fragments). The success rate was high in the diagnostic cases (20 of 24), but lower in the therapeutic cases (13 of 26). The complication rate was extremely low and the postoperative course was always uneventful. Flexible instruments offer a very good chance to explore the intrarenal collecting system. Both transureteral and percutaneous flexible nephroscopies are feasible and effective procedures. A laser can be used well in this area.