When a patient with a parapneumonic pleural effusion is first evaluated, a therapeutic thoracentesis should be performed if more than a minimal amount of pleural fluid is present. Fluid obtained at the therapeutic thoracentesis should be gram-stained and cultured and analyzed for glucose, pH, LDH, white blood cells, and differential cell count. If the fluid cannot be drained because of loculations, a chest tube should be inserted and thrombolytic agents administered. If the pleural fluid recurs after the initial therapeutic thoracentesis but the patient is doing well clinically and the initial pleural fluid glucose was greater than 60 mg/dL; the pH, greater than 7.2; the LDH, less than three times the upper normal limit for serum and the cultures are negative; he or she can be observed. If one or more of the aforementioned criteria are not met, a second therapeutic thoracentesis should be performed, with repeat diagnostic evaluations of the pleural fluid. If the fluid recurs a second time, a small chest tube should be placed if the pleural fluid glucose and pH were lower and the LDH higher on the second thoracentesis than on the first thoracentesis. Patients with loculated-parapneumonic effusions should be treated with tube thoracostomy and thrombolytic agents. If drainage is incomplete, thoracoscopy, with breakdown of adhesions and debridement of the pleural space, is indicated. If thoracoscopy is unsuccessful, then thoracotomy, with decortication, is indicated unless the patient is too debilitated.