Objectives ' The primary aim of the study was to investigate whether there is a difference in plasma B-type natriuretic peptide (BNP) levels among the left ventricular systolic dysfunction caused by different types of heart disease. Methods and results ' Plasma BNP was measured in patients with left ventricular systolic dysfunction as a result of mitral valve regurgitation (n=26), hypertension (n=36), coronary heart disease (n=37) and dilated cardiomyopathy (n=32). The left ventricular end-diastolic diameter and ejection fraction were assessed with echocardiography. The valvular heart disease group had more women and was younger (p < 0.05). There was no significant difference in the New York Heart Association functional class, left ventricular end-diastolic diameter and ejection fraction among the four groups (p < 0.05). The average plasma BNP was also similar among the four groups of patients. In each group, a significant correlation between the levels of BNP and the left ventricular end-diastolic diameter or ejection fraction was identified (p < 0.001). Conclusion ' Plasma BNP concentrations during left ventricular systolic dysfunction are associated with left ventricular diameter and function, but they are not determined by the causes of the heart failure.