The side effects of indomethacin for ductal closure in preterm neonates (e.g. increased incidence of necrotizing enterocolitis, decreased cerebral blood volume and transient renal failure) have led clinicians to seek a safer alternative. Intravenous indomethacin and ibuprofen appear to be equally effective for patent ductus arteriosus closure, but oral ibuprofen remains an experimental option with theoretical advantages yet with potential side effects. We herein report a case of transient but severe acute renal failure developing in a preterm infant in whom oral ibuprofen was used and discuss the safety of this drug in relation to its pharmacokinetics.