The infectious effusion, one of the most frequent causes of pleural effusions in the clinical practice, is a sign of complication of the pneumonic disease. The early recognition of the parapneumonic effusion is crucial to determine the best treatment form and reduce the risk of morbidity and mortality. The evolution in the diagnostic methods and the contribution of several studies published in the literature allowed to establish evidence-based guidelines that are used to guide the treatment of the parapneumonic pleural effusion and empyema.