The objective of the study was to evaluate the risk of asthma in children who had undergone an adenoidectomy, an operation frequently performed on children with glue ear or recurrent otitis media. Two surveys were carried out, a nation-wide questionnaire returned by 483 individuals (survey A) and a survey of hospital discharge records involving 1616 children who had undergone an adenoidectomy and 161 control children who had undergone probing of the nasolacrimal duct due to congenital obstruction (survey B). The questionnaire (survey A) showed that an adenoidectomy before the age of 4 years was associated with asthma (OR 3.19, 95% CI 1.25; 8.13) and with allergy to animal dust (OR 2.50, 95% CI 1.27; 4.95). In survey B, asthma diagnosis was retrieved from the national asthma register. It showed also that adenoidectomy at an early age was associated with an increased risk of asthma (OR 6.74, 95% CI 2.99; 15.2). There was an association between asthma and adenoidectomy, even before adenoidectomy had actually been performed. The risk of asthma was highest among children who had had adenoidectomy because of recurrent otitis media. The observed association between an adenoidectomy and asthma may be explained by an underlying factor predisposing to both recurrent otitis media and asthma.