Objective: Risk of childhood asthma is increased in children with recurrent otitis media. This may be associated with recurrent respiratory tract infections in these children, but the role of adenoidectomy, a frequent operation during childhood, is unknown. Therefore, the role of adenoidectomy in the development of atopy and respiratory function changes characteristic of asthma was evaluated. Design: Randomised controlled study. Setting: Tertiary care centre. Patients: 166 children aged 12–48 months who had recurrent or persistent otitis media and who were followed-up for 3 years after randomisation. Intervention: Randomisation to undergo insertion of tympanostomy tubes with or without adenoidectomy. Main outcome measures: The primary outcome measure was exercise-induced bronchoconstriction as evaluated by impulse oscillometry. The secondary outcome measures were bronchial inflammation as evaluated by exhaled nitric oxide and atopy as evaluated by skin prick tests. During the 3-year follow-up period otitis media episodes were documented in patient diaries. Results: Adenoidectomy did not significantly influence baseline lung function, exercise-induced bronchoconstriction, exhaled nitric oxide concentration, the development of positive skin prick tests, or doctor-diagnosed asthma. Adenoidectomy did not significantly prevent otitis media. Recurrent otitis media (⩾4 episodes) during the first follow-up year was associated with an abnormal exercise-induced bronchoconstriction (OR 6.62, 95% CI 1.27 to 34) and an elevated exhaled nitric oxide concentration (OR 3.26, 95% CI 0.98 to 10.8) regardless of adenoidectomy. Conclusions: Adenoidectomy did not promote asthma or allergy. Recurrent respiratory tract infections during early childhood are associated with the risk of bronchial hyper-reactivity.