How- ever, limited direct evidence from clinical trials is available with which to assess the efficacy of RAAS in children with CKD. In healthy children with hypertension, a number of clinical trials have examined the safety and efficacy of Small, uncontrolled studies have shown stable kidney function in children with CKD treated with ACE-Is Kidney dysfunction that is hemodynamic in origin has been more commonly associated with the use of ACE-Is and ARBs than with other anti-hypertensive agents. Additionally, since elevations in serum potassium levels have also been observed, counselling about potassium intake and addition of thiazide or loop diuretics are sometimes Although analysis of registry data from the ItalKid Project database failed to show clear evidence of ACE-I efficacy in slowing the progression of CKD,311 other observational evidence shows that ACE-Is are associated with lower urine protein levels349 and that BP control in childhood CKD is superior with anti-hypertensive regimens containing an ACE-I or ARB.312 In a small trial, an ARB was more effective at lowering urine protein levels than a calcium- The only study to date that has compared ACE-Is and ARBs in children found that urine protein levels were similarly reduced with the ACE-I enalapril and the ARB As in adults, ARBs may be more tolerable than ACE-Is in children, with fewer adverse events such as cough, angio- neurotic edema, and hyperkalemia but this has not been systematically studied in large trials. Combination therapy with ACE-Is and ARBs may be used for additive anti- proteinuric and renoprotective effects, but this approach has rarely been studied in children. 