Progress in neonatal medicine 1 has created an increased demand for life-support systems for the critically ill infant, in whom acute renal failure is a common complication. We have modified techniques for hemodialysis for use in the small child. 2 We describe hemodialysis of a 2-kg infant and discuss the indications for hemodialysis in small babies. Report of a Case .—The patient was one of female twins, with a birth weight of 2,100g at 34 weeks' gestation. She experienced a paroxysmal cough, tachypnea, and slightly inflamed conjunctivae at 4 weeks of age. The serum creatinine level was 0.3 mg/dL. Initial viral and bacterial cultures were negative. She subsequently experienced hyponatremia, focal seizures, and Coombs-negative hemolytic anemia, and hypertension, oliguria, and thrombocytopenia developed, with rising BUN and creatinine levels. At 7 weeks of age, she weighed 2,600g and was edematous and cachectic. The serum potassium concentration was 6.2 mEq/L and the