Pleural empyema represents a severe complication of community acquired pneumonia with an incidence of 0.6% among hospitalized children. Clinical manifestations of picture may be different in infants and young children and it should always be suspected in a child with pneumonia without significant clinical improvement after 48 hours of antibiotic treatment. The most common microorganism associated with empyema is Streptococcus pneumoniae, especially in children under 5 years of age. Chest radiograph is the gold standard for diagnosis but chest ultrasonography, and in some cases chestCT, may be necessary to study features and evolution of the pleural fluid in order to guide therapeutic choices. In most cases small pleural empyema responds to antibiotics alone. However in severe and extensive cases, drainage and invasive treatments, like video-assisted thoracic surgery (VATS) and thoracotomy, became necessary. Due to the early start of antibiotic therapy, blood and pleural fluid cultures may result negative; in these cases only the use of molecular techniques, like polymerase chain reaction in biological fluids, may determine the etiology of the infection. Here we report the case of previously healthy 8-years-old boy with an important and severe pleural empyema as a complication of S. Pneumoniae pneumonia, that did not respond to antibiotic therapy and thoracocentesis and for which decortication has been necessary. In our patient only molecular analysis on pleuric fluid has allowed us to define the etiology of the process
