Abstract Background: The finding of an exudative effusion usually requires an extensive diagnostic workup, leading to an unnecessary exposure to invasive and expensive diagnostic procedures. Thus a strategy of identifying pleural effusions due to heart failure and possibly avoiding unnecessary diagnostic thoracentesis and/or further diagnostic procedures would be an attractive and potentially beneficial approach [6]. NT-proBNP measured in serum is a sensitive marker of cardiac dysfunction and proven to be a useful tool in the diagnosis of acute and chronic systolic and diastolic left ventricular heart failure [7,8]. Purpose: The present study was conducted to assess the diagnostic value of NT-proBNP in the differentiation of cardiogenic and non cardiogenic pleural effusion. Patients and methods: Forty patients with pleural effusion were included in this study. Twenty patients with cardiogenic pleural effusions (pleural effusion due to cardiac cause) and 20 patients with non cardiogenic pleural effusions (pleural effusion due to non cardiac cause). All patients were subjected to full history, clinical examination, investigation to detect the etiology of the pleural effusion and measurement of serum and pleural fluid NT-proBNP. Results: In this study we found that pleural fluid NT-proBNP levels were significantly higher in patients with cardiogenic pleural effusions than that of patients with non cardiogenic pleural effusions (Mean ±SEM, 5231± 671.1 and 628.8± 120.1 respectively, P value < 0.0001). Also NTproBNP levels in the serum of the patients with cardiogenic pleural effusions were significantly higher than that of patients with non cardiogenic pleural effusions (Mean± SEM,4792± 612.7, and 604.0 ± 120.1 respectively, P value