St reptococcus pyogenes is an uncommon cause of community-acquired pneumonia in children. Further, its clinical course in comparison to pneumonia caused by Streptococcus pneumonia has not been previously highlighted.We reviewed medical records of children 0-18 years of age from April 1983 to April 2005, with discharge diagnoses of invasive disease caused by group A streptococcus (GAS) (Streptococcus pyogenes), or Streptococcus pneumonia (SP) or pneumonia. Data were extracted from the charts, and a comparison of clinical characteristics between the 2 etiologies was performed. Confirmed disease required blood or pleural fluid isolates. Patients with single isolates of GAS in tracheobronchial secretions or sputum were classified as having presumed disease caused by GAS. Patients with confirmed disease due to GAS and SP were compared with respect to clinical characteristics.Of 103 patients with invasive GAS disease, 12 (11.6%) had confirmed GAS lobar pneumonia. In addition 7 patients had presumed GAS pneumonia. There were 54 patients with confirmed SP pneumonia. Most children who had GAS pneumonia were healthy and recovered completely. Compared with patients with confirmed SP pneumonia, those with confirmed GAS pneumonia had more frequent and larger effusions, more culture positive effusions, had prolonged fever, and had longer hospitalizations. There was not an increasing trend to GAS pneumonia over the 22-year period. There was not a predominant serotype responsible for the pneumonias.Lobar GAS pneumonia represents approximately 11% of all cases of invasive disease in this institution during a 22-year period. Compared with patients with SP pneumonia, it appears to cause more effusions and morbidity. The organism is also more frequently recovered from pleural fluid.