Percutaneous antegrade pyelography and percutaneous nephrostomy can be easily performed using CT guidance. CT provides cross-sectional images which facilitate accurate needle placement into the renal pelvis. CT is capable of detecting subtle density differences within the tissues so that even renal pelvises which do not contain contrast material and are not dilated can be accurately punctured. In addition to these procedures, CT accurately displays the perinephric space so that assessment of complications is possible. Four of five attempted percutaneous nephrostomies and two antegrade pyelograms were successfully performed using CT gudance.