Right ventricular (RV) failure is a common problem for adults with systemic right ventricles or volume-overloaded right ventricles. The utility of B-type natriuretic peptide (BNP) levels for diagnosis and prognosis is now well documented in adults with acquired left ventricular (LV) systolic dysfunction, but not in the setting of RV failure. BNP levels were evaluated in adults with RV failure due to congenital heart disease and compared with levels in adults with acquired LV dysfunction and adults without structural heart disease.