B-type natriuretic peptide has been identified as a potential non-invasive marker of allograft rejection but the evidence supporting an absolute correlation ofthis neurohormone's elevation with cellular rejection and allograft dysfunction is weak. A within-individual change over time has been shown to provide a more accurate measure of acute rejection and may support the use of empiric therapy prior to rejection confirmation by endomyocardial biopsy. Identifying a noninvasive approach to the detection of rejection and developing a clinical practice guideline based on this has the potential to decrease risk, blunt cost, and provide those who care for this population with an adjunct method to recognize significant rejection, thereby assisting in the diagnosis and treatment of a potential life-threatening situation.