Patent ductus arteriosus (PDA) is frequent in neonates with gestational age of less than 28 weeks. Clinical and echocardiographic signs define hemodynamic significance of PDA, but do not reveal the need for PDA intervention in the first days of life. B-type natriuretic peptide (BNP) has been proposed as a screening tool for PDA in preterm infants. To determine whether BNP can predict the need for PDA intervention, plasma BNP was measured by chemiluminescence immunoassay in 67 preterm infants <28 weeks (median 26) on the second day of life (DOL) in a prospective blinded study. PDA intervention was based on specified clinical and echocardiographic findings. Twenty-four patients (intervention group) received treatment for PDA and 43 patients (controls) remained without intervention. BNP concentrations were higher in the intervention (median 1069 pg/ml) than in the control group (247 pg/ml, p<0.001). BNP correlated positively with ductal size (R = 0.46, p<0.001) and LA/Ao- ratio (R = 0.54, p<0.001). In conclusion, plasma BNP proved to be a good predictor for ductus intervention (area under the curve: 0.86) with the best cutoff at 550 pg/ml on the second DOL in ventilated infants less than 28 weeks gestation (sensitivity: 83%; specificity: 86%; positive predictive value: 77%; negative predictive value: 90%).