Use of the Collings knife electrode for percutaneous access in difficult endourology cases. Percutaneous endourological techniques for the removal of upper urinary tract calculi and for the closed treatment of ureteropelvic junction obstruction are well described. These techniques are dependent on satisfactory percutaneous access and nephrostomy tract dilation. We used the Collings knife electrode for the creation of a nephrostomy tract in 17 patients (19 renal units) with difficult percutaneous access due to scarification, or the inability to advance a guide wire sufficiently for stabilization and dilation by conventional means. A nephrostomy tract was established successfully in all 19 procedures requiring an average of 12 minutes. Two major complications occurred that required blood transfusion and an open operation. Endourological treatment was successful in the remaining 17 cases. We believe that this technique provides an alternative to an open operation when standard access and dilation methods for endourological procedures are unsuccessful. 