In patients with primary hyperoxaluria (PH), deficiency of hepatic enzymes important in disposition of glyoxylate results in marked hyperoxaluria. Calcium oxalate crystals and high oxalate concentrations in the renal filtrate result in inflammation and injury in the renal parenchyma. Loss of renal function over time is characteristic, with end stage renal failure occurring in half the patients by age 35 years, but as early as infancy in some patients. Experience in animal models of hyperoxaluria, and from other renal diseases, supports a role for ACEI and ARB medications in ameliorating inflammation and injury thus providing a renal protective effect.