The best results in percutaneous renal calculus removal are in patients with solitary pelvic stones and dilated collecting systems. Calyceal and/or infundibular calculi and ureteral calculi constitute more complex problems and are less successfully removed. Placement failure of the nephrostomy tube, and inability to gain access to calyceal calculi, and to engage impacted stones are the usual causes for unsuccessful procedures. To try to improve overall success we inserted occlusion balloon catheters prior to nephrostomy insertion in 60 of 71 patients. In a select group of 23 patients with a small renal pelvis and large calculi or infundibular calculi or patients with ureteral calculi, overnight application of 20 cm of hydrostatic pressure through the ureteric catheter led to marked dilatation in all instances. In all other patients the occlusion balloon catheter was placed immediately prior to the definitive nephrostolithotomy procedure. These ureteral catheters allow for better opacification and for dilatation of a small collecting system thereby facilitating the placement of the nephrostomy tube. They permit manipulation of calyceal and especially ureteral calculi. Placement of ureteral occlusion catheters is a safe adjunct to nephrostolithotomies and, in our experience, resulted in increased overall success.