OBJECTIVE B-type natriuretic peptide (BNP) is a neurohormone secreted from cardiac ventricles in response to ventricular strain. The aim of present study was to evaluate the role of BNP in the diagnosis of the right ventricular (RV) dysfunction in acute pulmonary embolism (PE). METHODS BNP levels were measured in patients with acute PE as diagnosed by high probability lung scan or positive spiral computed tomography. All patients underwent standard echocardiography and blood tests during the second hour of the diagnosis. RESULTS Forty patients diagnosed as acute PE (mean age, 60.4 +/- 13.2 years; 62.5% women) were enrolled in this study. Patients with RV dysfunction had significantly higher BNP levels than patients without RV dysfunction (426 +/- 299.42 pg/ml vs. 39.09 +/- 25.22 pg/ml, p < 0.001). BNP-discriminated patients with or without RV dysfunction (area under the receiver operating characteristic curve, 0.943; 95% CI, 0.863-1.022). BNP > 90 pg/ml was associated with a risk ratio of 165 (95% CI, 13.7-1987.2) for the diagnosis of RV dysfunction. There was a significant correlation between RV end-diastolic diameter and BNP (r = 0.89, p < 0.001). Sixteen patients (40%) were diagnosed as having low-risk PE, 19 patients (47.5%) with submassive PE and five patients (12.5%) with massive PE. The mean BNP was 39.09 +/- 25.2, 378.4 +/- 288.4 and 609.2 +/- 279.2 pg/ml in each group respectively. CONCLUSIONS Measurement of BNP levels may be a useful approach in diagnosis of RV dysfunction in patients with acute PE. The possibility of RV dysfunction in patients with plasma BNP levels > 90 pg/ml should be strongly considered.