Pleural effusions are common in cancer patients, developing either from the malignant condition or from unrelated causes, such as congestive heart failure, pulmonary infarction, or infection. Diagnosis of malignant pleural effusion rests on demonstration of the presence of malignant cells in the pleural fluid or pleural biopsy specimen. Treatment is usually aimed at relief of symptoms rather than at the underlying malignancy. Specific therapeutic measures include thoracentesis, chest tube drainage, pleurodesis with chemicals or biologic agents, radiation and systemic chemotherapy, surgical pleurodesis, and pleuroperitoneal shunt. These should be supplemented by ancillary measures to maintain fluid and nutritional balance and prevent complications.