OBJECTIVE: The etiology of acute lower respiratory tract infection (LRTI) in children in Wenzhou City remains poorly defined. This study investigated the etiological agents responsible for acute LRTI and patterns of the antibiotic resistant bacterial pathogens in children with acute LRTI from Wenzhou City. METHODS: Lower respiratory tract secretions were obtained from 454 children with acute LRTI (aged 1 month to 10 years, median age 6 months) within 24 hrs after admission for bacterial culture. Meanwhile respiratory viruses were detected by the Direct immunofluorescence (DIF) assay. The K-B method was applied for the drug susceptibility test. RESULTS: Etiological agents were identified in 297 cases out of 454 patients (65.4%. Viral pathogens were identified in 229 cases (50.4%), bacteria in 135 cases (29.7%) and mixed viral-bacterial infections in 67 cases (14.8%). The isolating rate of Respiratory syncytial virus (RSV) was the highest (180 cases, 39.6%) in all of the samples. The isolating rates of other viral pathogens were as follows: Parainfluenza virus 3 type (PIV3) (6.6%), Adenovirus (2.2%), Influenza A (0.9%) and Influenza B (0.7%). Of the 135 strains of bacterial pathogens, 19 kinds of bacterial pathogens were isolated. The predominant isolate was Klebsiella pneumoniae (K. pneumoniae) (9.9%), followed by Escherichia coli (E.coli) (4.4%), Streptococcus pneumoniae (S. pneumoniae) (4.2%) and Staphylococcus aureus (S. aureus) (4.2%). The isolating rates of K. pneumoniae and E.coli with extended-spectrum beta-lactamases strains (ESBLs) positive were 42.2% and 65.0%, respectively. The pathogens isolated of the first 5 places in children with acute LRTI under six months were RSV, K. pneumoniae, PIV3, E.coli and S. aureus in turn. RSV, PIV3, S. pneumoniae, K. pneumoniae and E.coli were found to be the pathogens of the first 5 places in children with acute LRTI between six months and three years. The resistant rates of K. pneumoniae and E.coli to ampicillin were 97.8% and 75.0%, respectively. K. pneumoniae and E.coli with positive ESBLs were resistant to cephalosporin. The resistant rates of S. pneumoniae to erythromycin and penicilin were 100% and 68.4%, respectively. The resistant rates of S. aureus to erythromycin and penicillin were 94.7% and 89.5%, respectively. CONCLUSIONS: RSV is the most common pathogen responsible for acute LRTI in children in Wenzhou City, followed by K. pneumoniae and PIV3. The rate of antibiotic resistance of common bacteria and the isolating rate of Gram-negative bacillus with ESBLs positive are high.