Acute renal failure (ARF) can be defined as the sudden loss of adequate renal function to clear metabolic wastes and maintain normal fluid and electrolyte balance. ARF may occur in otherwise healthy children, may complicate underlying chronic kidney disease, or may result from multiorgan disorders. The underlying cause of the renal injury remains the major factor that determines outcomes for patients with ARF. Overall mortality in children with ARF varies from 8% to 89%, with greater than 50% mortality associated with three-organ system failure. Management of the adolescent with ARF ranges from conservative management in mild cases to more intensive care in hospitalized patients with complications of fluid overload, hypertension, metabolic acidosis, or life-threatening hyperkalemia.