In Alassad Hospital we studied a population of 70 patients with pleural effusion for a period from August 2014 to Agust 2015 . The patients were 40men(57.1%) and 30 women(42.9) . According to the criteria used , 23(32.9%)patients were transudative effusions , and 47(67.1%)had exudative effusions . In our study we measured the level of cholesterol in the pleural fluid to assess the role of this measure in differentiating between transudativ and exudative effusion and the different causes of the effusion . We found that : pleural fluid cholesterol levels were significantly lower in the transudative than in exudative effusions ( 10.702±21.8 mg/dL and 32.67±69.39 mg/L respectively ) , but Light's criteria is better than level of cholesterol in pleural effusion to differentiate between the two types of effusions . but the stsatistic result improved when we add cholesterol into lights criteria . In the exudative effusion with lymphocytic cholesterol level more than 72.5 mg/dL is a strong suggestion for tuberculosis effusion , whether the level lower suggestive of malignant for exudative effusions . So , levels of cholesterol in pleural effusion can narrow the differential diagnosis of pleural effusions and help for perfecting the results .