Abstract 
 Recurrent attacks of tonsillitis are a common worldwide problem and the best treatment of choice after failure of medical therapy is a tonsillectomy. The large numbers of patients that presented with recurrent attacks of tonsillitis and associated with high antistreptolysin O (ASO) titer level due to group A beta hemolytic streptococcal (GABHS) tonsillitis will have serious complications as glomerulonephritis and rheumatic fever. The aim of study: to evaluate the effect of tonsillectomy on elevated ASO titer.
 Patients and methods: Prospective non-randomized clinical study was performed at Al-Jumhory teaching hospital, Mosul, Iraq; for the period from January 2021 to January 2022. that included seventy patients for whom tonsillectomy was indicated. There were 45 females and 25 males, the age range from 3 to15 years old and the mean age was7.63year. Positive throat swab for group A beta hemolytic streptococcal (GABHS) and elevated ASO titer level (≥200 IU/ml). Postoperative follow up of the patients were processed for six months.
 Results: seventy patients included in the study, presented with recurrent attacks of tonsillitis, with positive throat swab for GABHS and elevated ASO titer level (≥200 IU/ml), age between 3 to 15 years old .Follow up of the patients for six months after tonsillectomy had been shown that there is a significant decrease in ASO titer level in comparison to preoperative level measures (p <0.001 )
 Conclusion: The most important conclusion from the result of our study that tonsillectomy lead to significant reduction in ASO titer level.