Pleural effusion is a common clinical problem. The volume of the pleural fluid can increase dramatically with most pathologic conditions affecting the pleura. It is useful to differentiate the pleural effusion into transudates and exudates. Traditionally, such differentiation is made using Light’s criteria, based on the protein and lactate dehydrogenase levels in pleural fluid and serum (Lee et al, 2006). Analysis of pleural fluid assists in the diagnosis of intra-thoracic and systemic disorders that cause pleural effusions. Nearly 75% of patients with pleural effusions gain either a definitive or presumptive diagnosis after asystematic analysis of pleural fluid. The need for further diagnostic studies depends on whether pleural fluid is classified by pleural fluid analysis as exudative or transudative in nature (Heffner, 2006). Proteolytic processes may play a role in the formation of pleural effusions by increasing vascular permeability, and therefore by facilitating fluid influx into the pleural space (Zucker et al, 1998). The presence and enzymatic activities of MMPs and TIMPs have been identified in pleural effusions (Hurewitz et al, 1992) and (Eickelberg et al, 1997).