The efficacy of nebulised sodium cromoglycate (SCG) used as a prophylactic treatment of wheezy bronchitis in children aged 1 to 4 years was evaluated in a multicentre double-blind placebo controlled, group comparative study. Fifty-four patients completed the 10-week trial (29 treated with SCG and 25 treated with placebo), preceded by 4-8 weeks baseline. Nebulised SCG did not prove significantly superior to placebo in reducing day wheezing, day coughing, or sleep disturbance due to wheezing or coughing at night. Neither was there significant difference in the use of supportive medicine (beta 2-agonist and theophylline) between the groups. Extra doctor visits, hospital admissions, and parental preference did not show significant difference either.