Elevated plasma N-terminal pro-brain natriuretic peptide levels have been demonstrated in patients with chronic valvular disease. To assess whether changes in N-terminal pro-brain natriuretic peptide levels after mitral, aortic, and double-valve replacement reflect changes in heart failure symptoms, a prospective observational nonrandomized study was undertaken in 24 consecutive patients (mean age, 55.3 ± 16.2 years; 58% male) undergoing mitral and/or aortic valve replacement. Mitral valve replacement was carried out in 12 patients, aortic valve replacement in 8, and combined mitral and aortic valve replacement in 4. N-terminal pro-brain natriuretic peptide measurements, echocardiography, and functional class assessment were performed before and 6 months after surgery. A decrease in N-terminal pro-brain natriuretic peptide at 6 months postoperatively was significantly associated with decreased left atrial dimension, left ventricular end-diastolic and end-systolic dimensions, increased ejection fraction, and improvement in functional class. Thus we can hypothesize that measurement of N-terminal pro-brain natriuretic peptide might allow early detection of any clinical deterioration as well as assessment of the long-term outcome in valve replacement patients.