Indomethacin is commonly used for the treatment of patent ductus arteriosus (PDA) but has renal failure as a main side-effect. Ibuprofen seems to be efficient in closing the ductus with less side-effects, but few studies are available in literature as regards its use in preterm infants. This study is a retrospective analysis of clinical data in order to compare the efficacy and the renal tolerability of ibuprofen and indomethacin administered to preterm infants with gestational age (GA) < or = 30 weeks for the treatment of PDA. From our data, ibuprofen results pharmacologically as efficient as indomethacin and could be an alternative in prematures. About renal tolerability, our data confirm that non-steroidal anti-inflammatory drugs treatment could affect at least transiently renal function. Moreover, indomethacin could be more nephrotoxic compared with ibuprofen, as creatinine concentrations normalize more slowly in this group, although the mean difference between the two drugs was not significant as our population sample was small. Further studies are needed to assess whether ibuprofen is really less nephrotoxic than indomethacin, in particular by examining carefully the correlation between GA and ibuprofen administration.