Pleurodesis aims to achieve a symphysis between parietal and visceral pleural surfaces, in order to prevent accumulation of fluid or air in the pleural space. Its major indications are malignant effusions and pneumothorax, and a re-expandable lung is essential for the success of the technique. Moreover, expectation of a reasonably long survival is important before attempting pleurodesis. A successful lung re-expansion is unlikely if the pleural pressure falls more than 20 cmH2O.L-1 of fluid removed, because there is a central bronchial obstruction or the lung is trapped by turnout and/or fibrin. Pleural fluid pH (7.20) is a good indicator of the presence of trapped lung; moreover, a successful pleurodesis is less likely when pH is low, and this parameter is also a good predictor for survival of the patients. Among the many sclerosing agents that have been used for pleurodesis, talc has achieved the best results, with an average success rate of approximately 90%. The cellular and biochemical mechanisms involved in pleurodesis may be specific to the agent used, however, they may all follow a common final pathway leading to activation of the pleural coagulation cascade, the appearance of fibrin networks, and the proliferation of fibroblasts. The details of these mechanisms are still unclear and need to be further elaborated.