B-type natriuretic peptide (BNP) is increasingly used in emergency departments to assess the cause of acute dyspnea and in cardiology to follow treatments and predict outcome. It is increasingly used in the intensive care unit in situations such as respiratory failure (acute pulmonary edema, exacerbation of chronic obstructive pulmonary disease and difficult weaning from ventilator) or when pulmonary embolism is suspected. BNP has also been used to assess alteration of myocardial function in sepsis. Plasma BNP is very high in septic-shock patients (>1000 pg/ml), which is suggested to relate to both myocardial stretch and to an alteration in one of the BNP clearance pathways. Whether BNP at admission or at discharge may predict outcome requires further investigation.