Pneumatoceles are thin-walled cavities most often caused by S. aureus. Pneumatoceles develop as sequelae of bacterial pneumonias in children. Although less than 3% of bacterial pneumonias in children result in formation of a pneumatocele, more than 80% of S. aureus pneumonias result in pneumatocele in the same population. Other organisms associated with pneumatocele formation include Streptococcus pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae, Serratia marcescens, Escherichia coli, group A streptococci, Mycobacterium tuberculosis, and Pseudomonas aeruginosa. Pneumatoceles rapidly develop in areas of previous consolidation. Because of the rapid growth and thin walls, these cavities can rupture into the pleural space, causing a tension pyopneumothorax. In such cases, insertion of a tube thoracostomy can be life saving. Most children present with symptoms typical of pneumonia, such as fever, cough, and dyspnea. The differential diagnosis for children presenting with these symptoms includes bacterial pneumonia, pneumatocele, pulmonary sequestration, cystic adenomatoid malformation, and bronchogenic cyst.