Background: Observational studies suggest that asthma/wheezing improve after adenotonsillectomy (AT). However, there is a paucity of RCT specifically studying the effects of AT in asthma/wheezing. Therefore, we conducted a post-hoc analysis of the Childhood Adenotonsillectomy Trial, the largest RCT of AT in children with obstructive sleep apnea (OSA) to test the hypothesis that AT would result in fewer wheezing episodes. Methods: In the CHAT study, 464 children with OSA, aged 5 to 9 years, were randomized to early AT (n=226) or watchful waiting with supportive care (WWSC) (n= 227). For this post-hoc analysis children were categorized as having “any wheezing” vs. “no wheezing” at baseline and at 7 months of follow-up. A multivariate analysis was conducted to evaluate the association between “any wheezing” at follow-up and treatment group after controlling for several potential confounders. Results: Children in the “any wheezing” group were predominantly black, had more allergic rhinitis, eczema, second-hand smoke exposure, more siblings and siblings with asthma, lower maternal education and family income than those in the “no wheezing group”. At baseline, wheezing characteristics were similar between AT and WWSC arms. At follow-up (at 7 months of the intervention) those in the AT arm had significatively less wheezing than those in the WWSC (22.4% vs. 43.8%, p=0.00001). However, the multivariate analysis of “any wheezing” vs. “no wheezing” at follow-up showed that the treatment arm was not associated with wheezing. Conclusion: This study demonstrated that AT has not effect on wheezing at 7 months of follow-up.