OBJECTIVE: To study the distribution of pathogenic microorganisms of community acquired pneumonia (CAP) in children. METHODS: Respiratory secretion and blood specimens were collected in 1 167 children with CAP within 4 hrs of admission. Mycoplasma pneumonia and Chlamydia trachomatis were detected by RT-PCR in respiratory secretion specimens. Respiratory syncytial virus (RSV-IgM) and Adenovirus (ADV-IgM) were tested using ELISA in blood samples. RESULTS: A total of 308 strains of bacteria were isolated from the respiratory tract secretions, with gram positive strains of 53.6% and gram negative strains of 46.4%. The top five bacteria strains detected were Streptococcus pneumoniae (35.1%), Escherichia coli (11.7%), Staphylococcus aureus (8.8%), Klebsiella pneumonia (6.5%) and Moraxelle catarrhalis (5.8%) in turn. Beta-lactamase and ESBLs producing strains accounted for 30.1% in the top five bacteria strains. The non-bacteria pathogens were found in 281 specimens (24.1%). Respiratory syncytial virus accounted for the most prevalent pathogen (19.3%). The mixed infection of respiratory syncytial virus and Streptococcus pneumoniae was common (35.2%). The infection rate from most of pathogenic microorganisms among children under the age of one was higher than that in children over one year old. CONCLUSIONS: Respiratory syncytial virus and Streptococcus pneumoniae are the major pathogens of CAP in children. The risk of pathogenic microorganism infections in children under the age of one is higher than that of children over one year old.［Chin J Contemp Pediatr, 2010, 12 (3):184-187］