BACKGROUNDCommonest causes of exudative pleural effusions are synpneumonic, tuberculous and malignant. Synpneumonic effusions are usually neutrophilic in fluid cytology, while the other two are lymphocyte predominant. Elevated pleural fluid adenosine deaminase can suggest a tuberculous aetiology in clinically suspected cases. Malignant effusions need a fluid cytology positive for malignant cells to make a diagnosis. If not yielding, invasive biopsies need to be done. This study was undertaken to find out a group of variables, which can predict malignancy in lymphocytic pleural effusions. Aim-To identify the best predictor of malignancy in lymphocytic pleural effusions. Settings and Design-This was a cross-sectional study done in the Pulmonary Medicine Department, GMC, Trivandrum during the year 2000.