Wheezing in early childhood is common, occurring in approximately 50% of children before the age of 6 years.' Understanding the role of respiratory viruses in triggering acute wheezing in children has been compromised by the lack of comparison groups in previous studies.(2) The objective of this study was to investigate the association (using a control group) of two common viruses-influenza virus and respiratory syncytial virus (RSV)-with acute wheezing among children, aged 1-7 years, with a past history of wheezing.