OBJECTIVE The aim of this study was to investigate the potential role of brain natriuretic peptide (BNP) levels in the assessment of functional status and right heart performance in primary pulmonary hypertension (PPH). BACKGROUND Primary pulmonary hypertension is a progressive disease leading to right heart failure and death. Right heart catheterization and maximal or submaximal exercise tests are employed to assess the course of the disease and the effect of therapeutic interventions. Additional noninvasive and reproducible parameters would be helpful to assess the status of patients with PPH. The natriuretic peptide system is up-regulated in PPH patients. Brain natriuretic peptide (BNP) is produced from the cardiac ventricles and elevated in PPH. The aim of our study was to evaluate the clinical significance of BNP in PPH patients. METHODS Correlation analysis was performed for plasma BNP levels of 28 PPH patients and World Health Organization (WHO) functional class (WHO-class), distance walked in 6 min, peak oxygen uptake (peak Vo(2)), and oxygen pulse during spiroergometry and various hemodynamic parameters, including pulmonary vascular resistance (PVR), pulmonary artery pressure (PAP), right atrial pressure (RAP), and cardiac index. RESULTS The BNP levels were inversely correlated with the 6-min walk (r = -0.70; p < 0.001) and peak Vo(2) (r = -0.61; p < 0.01), and positive correlation was observed with WHO-class (r = 0.79; p < 0.001). Moreover, BNP levels were also correlated to PVR (r = 0.61; p < 0.01), PAP (r = 0.48; p < 0.05), and RAP (r = 0.78; p < 0.01), and were inversely related to cardiac index (r = -0.48; p < 0.05). CONCLUSIONS Our data suggest that plasma BNP levels are closely related to the functional impairment of PPH patients and parallel the extent of pulmonary hemodynamic changes and right heart failure. Serial measurements of plasma BNP concentrations may help improve the management of PPH patients.