Thirthy-seven consecutive patients with acute decompensated heart failure (ADHF) admitted to emergency departments for acute dyspnea were investigated. Ten patients with acute exacerbation of chronic obstructive pulmonary disease and 10 patients with hypertension crisis were also included as controls. For each patient, a plasma amino-terminal pro-B-type natriuretic peptide (NTproBNP) concentration measurement was performed at admission, 4, 12, and 24 hours later, and on the day of discharge. In patients with ADHF, the observation of a progressive reduction to a complete relief of symptoms of heart failure was accompanied by a reduction of 58% of NTproBNP plasma levels on the day of discharge. Amelioration of symptoms was accompanied by improvement of physiologic parameters and New York Heart Association functional class. In the control population (chronic obstructive pulmonary disease and hypertension crisis patients), no significant variation of NTproBNP levels in comparison with those at admission was found at each time point. In conclusion, a plasma profile obtained with sequential measurements indicates that a significant decrease in NTproBNP levels is associated with the clinical improvement of patients with ADHF at the time of discharge.