B-type natriuretic peptides are predominantly synthesized in the ventricular myocytes. This is the response to volume overload or increased stress to the ventricular wall. Plasma B-type natriuretic peptide levels are elevated in patients with chronic renal failure due to reduced glomerular filtration and/or increased myocardial biosynthesis. Allograft renal transplantation significantly reduces plasma B-type natriuretic peptide. Our previous clinical observations have demonstrated that acute allograft renal rejection is associated with a sudden increase in plasma B-type natriuretic peptides. We hypothesized that plasma B-type natriuretic peptide may be used as a sensitive and specific biomarker for clinical diagnosis of acute allograft renal rejection.