This is a monoclonal antibody specific for NT-Pro BNP and can be used singly in a competitive immunoassay to measure the amount of this analyte in blood samples for the purpose of diagnosis or monitoring of congestive heart failure. In addition, it could be used in a sandwich immunoassay with a monoclonal or a polyclonal antibody which recognizes a different part of the NT-Pro BNP molecule. Monoclonal antibodies are well-defined reagents which can be produced continuously and consistently. Measurement of NT-ProBNP in human serum to aid in the diagnosis and monitoring of congestive heart failure.