AbstractRespiratory syncytial virus (RSV) is one of the pathogens generally associated with the common cold, lower respiratory infection, and exacerbation of asthma. Disodium cromoglycate (DSCG) is a safe and widely used drug for the prevention of bronchial asthma and allergic rhinitis attacks. The effect of DSCG on acute upper respiratory tract viral infections remains controversial. The purpose of the study was to investigate the effects of DSCG on parameters of RSV induced‐illness. Using a well‐characterized murine model of RSV infection, the effect of DSCG on RSV‐induced illness was evaluated by body weight, respiratory function, viral replication, level of IFN‐γ in lungs, serology, and histopathology. Mice treated with DSCG were protected against RSV‐induced weight loss. The baseline Penh in RSV‐infected mice treated with DSCG was less than that in mice treated with saline. In methacholine challenge, the increase in Penh in RSV‐infected mice treated with DSCG was suppressed to the same level as that in the mock‐infected group. Further, there were no differences in viral replication between the mice treated with DSCG and those treated with saline, and the level of inflammation observed in the lungs in RSV‐infected mice treated with DSCG was not as severe as that in mice treated with saline. These findings indicate that DSCG may be an effective agent for the prevention of RSV induced disease and the relief of symptoms of RSV infection. J. Med. Virol. 81:354–361, 2009. © 2008 Wiley‐Liss, Inc.