We analyzed 211 consecutive plasma B-type natriuretic peptide (BNP) measurements in 59 pediatric heart transplant patients along with echocardiographic and right ventricular endomyocardial biopsy samples. Patients with a biopsy specimen negative for rejection had significantly lower BNP levels than those patients with a biopsy positive (p </=0.04) for rejection. BNP significantly decreased with treatment (p </=0.007). BNP levels in the first year after heart transplantation in all patients were significantly greater than BNP levels after the first year in all patients (p <0.001).