We read with interest the report by Cataldi et al of the case-control study on acute renal failure in preterm infants in seven Italian neonatal intensive care units.¹ We have recently completed a one year study of acute renal failure (ARF) in 467 consecutive admissions to a tertiary neonatal referral unit. There were 5661 live births in the adjoining maternity unit over the year, and 47 admissions were from outborn patients (one surgical, 46 medical). We defined ARF as plasma creatinine >100 µmol/l at 48 hours of age based on published data of declining creatinine concentrations in infants of various gestational ages.² Forty one infants (8.8% of NICU …