We examined the utility of B-type natriuretic peptide (BNP) in the evaluation of pediatric orthotopic heart transplant recipients for allograft pathology by measuring the serum BNP levels at the time of either screening echocardiography and biopsy, or at the time of clinical rejection. There was a significant difference (p <0.0001) in the BNP levels in 37 patients in the group with evidence of pathology compared with those without evidence. There was also 100% sensitivity and 100% negative predictive value of BNP levels >100 pg/ml for identifying graft pathology.