['The utility of B-type natriuretic peptide (BNP) for detecting acute rejection (AR) is unclear. The purpose of our study was to evaluate BNP as a screening test for AR in pediatric heart transplant patients.', 'All endomyocardial biopsies (EMBs) with concurrent BNP levels from February 2004 through March 2007 at the study institution were reviewed and the association between BNP levels and acute rejection was assessed.', 'Eighty-six patients underwent a total of 560 EMBs. The median age at EMB was 10.5 years (interquartile range [IQR] 3.7 to 15.4 years). There were 59 episodes of AR, 32 (54%) occurring at <1 year post-transplant. BNP levels were higher in patients with AR, median 387 pg/ml (IQR 125 to 931 pg/ml), compared with those without AR, median 66 pg/ml (IQR 37 to 148 pg/ml) (p < 0.001). The receiver operating characteristic (ROC) curve for BNP demonstrated an area under the curve (AUC) of 0.82 (95% confidence interval [CI] 0.76 to 0.88) (p < 0.001). A BNP level of 100 pg/ml corresponded to a sensitivity of 0.85 (95% CI 0.73 to 0.92) and a negative predictive value (NPV) of 0.97 (95% CI 0.95 to 0.99) for detecting AR. The ROC curve for patients at >1 year post-transplant demonstrated an AUC of 0.86 (95% CI 0.80 to 0.93) (p < 0.001), and a BNP level of 100 pg/ml corresponded to a sensitivity of 0.96 (95% CI 0.79 to 0.99) and NPV of 0.994 (95% CI 0.962 to 0.999) for detecting AR.'] Is b-type natriuretic peptide a sensitive screening test for acute rejection in pediatric heart transplant patients?