Successful definitive (complete) percutaneous renal procedures in the pediatric age group were performed in 97 per cent of antegrade pyelograms, in 94 per cent of ureteral perfusions (Whitaker test), in 98 per cent of nephrostomies, and 100 per cent of both retroperitoneal fluid drainages and renal aspiration biopsies. Significant complications, or those necessitating specific treatment or prolonged hospitalization, were 1.1 per cent. 0.7 per cent, 15.2 per cent, 0 per cent, and 0 per cent, respectively, for the above procedures. Not surprisingly, certain operators are more adept than others at successfully performing procedures and at avoiding some but not all complications (see Tables 2 and 3). Proper training, experience, and adherence to basic principles are important. However, there were no deaths, no kidneys lost, and no transfusions or operations required as a result of any complication from the pediatric percutaneous renal procedures; correction of any existing blood coagulation disorder is necessary prior to their performance to avoid potentially fatal hemorrhage.