Content and Objectieve: Many children with acute lower respiratory tract infection (ALRI) present to the emergency ward with concurrent wheezing. A chest x-ray is often requested to rule out pneumonia. We assessed inter observed agreement in interpreting x-rays on such children. Designs and Setting: Prospective consecutive case study at Instituto de Salud del Niño Lima, Peru. Methods: Chest x-rays were obtained from eligible children younger than two years olds with ALRI an concurrent wheezing who were seen in the emergency ward of a nationwide pediatric referal hospital. The x-rays were read independently by three different pediatric residents who were aware only that the children had a respiratory infection. All the children had received inhaled beta-adrenergic agonists before undergoing chest x-rays. Labor and complicated pneumonia cases were excluded from the study. Resuts: Two hundred x-rays were read. The overall kappa indexd was 0.2. The highest individual kappa values for specific x-ray findings ranges from 0.26 to 0.34 for rib horizontalization and from 0.14 to 0.31 for alveolar infiltrate. Inter-observer variation was intermediate for alveolar infiltrate (kappa 0.14 to 0.21) and for air bronchogram (kappa 0.13 to 0.23). Reinforcement of the bronchovascular network (kappa 0.10 to 0.16) and air trapping (kappa 0.05 to 0.20) had the lowest agreement. Conclusions: There was poor inter-observer agreement for chest x-ray interpretation on children with ALRI and concurrent wheezing seen at the emergency ward. This may preclude reliable diagnosing of pneumonia in settings where residents make management decisions regarding sick children. The effects of training an inter-observer variation need further studies. Copyright © 2007, Associação Paulista de Medicina.