Malignant pleural effusions result from neoplastic infiltration of the pleural surface. Malignant pleural effusions most commonly arise from lung carcinoma, breast carcinoma, and lymphoma. The true incidence of malignant pleural effusion is unknown but up to 15% of patients with lung cancer and 11% of patients with breast cancer will have a malignant effusion at some time during the course of disease. Most patients will have varying degrees of dyspnea at presentation, which is the main symptom related to the effusion. On chest radiograph and computed tomography, there will be evidence of an effusion as well as potential parenchymal lesions consistent with a lung primary tumor or parenchymal metastases. Diagnosis is established by demonstration of malignant cells in the pleural fluid or pleural tissue. Malignant pleural effusions result from metastases to the visceral pleural surface with secondary seeding of the partial pleural surface. In addition to treatment of the primary tumor, management consists primarily of palliation of dyspnea via pleurodesis by means of a chest tube-administered sclerosant agent or talc poudrage by way of medical thoracoscopy.