<p class="abstract"><strong>Background:</strong> Adenotonsillectomy is one of the commonest surgical procedures performed by the otolaryngologists. The immunological effects of adenotonsillectomy have not been studied extensively. Some researchers have found decreased immunoglobulin levels after adenotonsillectomy while others have not reported any significant changes. The present study aimed to evaluate the changes in humoral immunity in patients undergoing adenotonsillectomy before and after surgery as measured by serum immunoglobulin levels.</p><p class="abstract"><strong>Methods:</strong> The study designed was a prospective observational case-control study conducted at Yenepoya Medical College Hospital, a tertiary referral hospital, Mangalore, Karnataka. A total of 25 patients in the age range 5-15years who underwent adenotonsillectomy for chronic adenotonsillitis and 25 age and sex matched controls participated in the study. Serum immunoglobulin G, A and M (IgG, IgA and IgM) levels were estimated 24 hours prior and 4 weeks after adenotonsillectomy. The statistical analysis used was non-parametric tests.</p><p class="abstract"><strong>Results:</strong> Serum levels of IgG, A and M were found to be significantly higher in patients with chronic adenotonsillitis. The levels of all the three immunoglobulins decreased to normal one month post-operatively.</p><p><strong>Conclusions:</strong> Removal of infected tissue and chronic antigenic stimulation resulted in restoration of serum immunoglobulin levels to normal. While chronic adenotonsillitis contributed to changes in humoral immunity as reflected by higher serum immunoglobulin levels, adenotonsillectomy enabled restoration of the immunoglobulin levels to normal.</p>