Abstract: Obj ective To observe the detection rate of pathogens in hospitalized children with acute respiratory infection (ARI)from the year 2011 to 2013 in Changzhou region.Methods Hospitalized children with ARI (a total of 6 366 cases)in Changzhou First People′s Hospital from January 2011 to December 2013 were enrolled.Clinical materials of children were collected.Serum legionella pneumophila,mycoplasma pneumoniae,Q fever rickettsia,chlamydia pneumoniae,aden-ovirus,respiratory syncytial virus,influenza A virus,influenza B virus,para-influenza virus types 1/2 and IgM-3 antibody were detected by using indirect immuno-fluorescence assay (IFA).The detection of pathogens was analyzed,and detection rate of each pathogen in children with different ages,seasonal distribution and causative condition of each pathogen were analyzed as well.Results At least one kind of pathogen was detected positively in 1 ,850 cases with the total detection rate of 29.06% (1850/6366 ).Mycoplasma pneumoniae was the most common pathogen with the detection rate of 2 5 .3%(1 4 2 3 /6 3 6 6 ).The median age of children infected by respiratory syncytial virus and adenovirus was less than the median age of overall children (P<0 .0 1 ).The respiratory syncytial virus was detected highest in the group with the age of 1 to 6 months (3.58%,14/391);mycoplasma pneumoniae was detected the most in the rest groups with other ages.In addition to Q fever pathogen rickettsia,chlamydia pneumoniae,the rest of the pathogens were significantly seasonal.Mycoplasma pneumoniae infections were the most common in acute respiratory infection,laryngitis,bronchitis,bronchiolitis,bronchial pneumonia and bronchial asthma with infection.Conclusion Respiratory syncytial virus is the common cause of respirato-ry tract infection in hospitalized children with ARI in Changzhou.Different pathogens have dif-ferent age distributions with distinguished seasonal and disease distribution characteristics.