The clinical use of brain natriuretic peptide (BNP) in patients after cardiac transplantation remains to be defined. Over the last decade, a series of small studies have been performed to determine any potential use of this assay in the assessment of allograft function and prognosis. From the available evidence, it appears that a low BNP level in transplant recipients has a high negative predictive value for death. Why patients with higher BNP levels should be disadvantaged appears to be multifactorial. BNP titer may be influenced by severe rejection episodes and diastolic dysfunction, and possibly intracardiac pressure derangement. Although the concept of using a simple blood test to assess these patients sounds very attractive, further work is needed to define the exact role of this assay. Presently, it cannot be confirmed whether BNP can replace any of the current methods of assessing allograft performance and prognosis after transplantation.