The first diagnostic step in pleural effusions is the separation of transudates from exudates. We aimed in present study to investigate the value of HDL/LDL ratio for distinguishing between pleural exudates and transudates. Pleural fluids (PF)from 121 patients, including 28 transudates and 93 exudates were analyzed. The levels of cholesterol, HDL cholesterol and LDL cholesterol in PF were measured. The HDL/LDL ratio was calculated. HDL/LDL ratio found significantly higher in transudates than exudates (p= 0.001). Receiver operating characteristic (ROC) curves were generated and the cut off points determined to the highest level of accuracy and precision. The HDL/LDL ratio was to maximize sensitivity over specificity in the diagnosis of a transudative effusion. The usefulness of HDL/LDL ratio for identifying transudates was evaluated in terms of sensitivity and specificity. The value of pleural HDL/LDL ratio that best differentiated between transudates and exudates was 0.6 (sensitivity 89%, and specificity of 79%). Measurement of HDL and LDL in PF and calculating of HDL/LDL ratio can be proposed to aid for differentiation between pleural exudates and transudates with advantage of not requiring serum levels.