Objective: The main objective of this study was to find out the most common organism affecting the tonsils in recurrent tonsillitis.

Methodology: This was a prospective study consisting of total number of 50 patients, conducted in the ENT department of Dhulikhel Hospital, KUTH, Dhulikhel, Nepal. The study period was of one year and three months (March 2004 to April 2005).

Results: Total numbers of 50 patients were selected, of which 32 were of acute tonsillitis and 18 were taken as control. Among these males were 32 and females were 18. The age group was from 3 years to 64 years. Throat swabs of patients were taken by aseptic method and were sent to the laboratory immediately. Among the infected tonsils the most common organism was Streptococcus viridans followed by Streptococcus pneumoneae and Morexella catarrhalis. The third most common was Beta haemolytic streptococci whereas Micrococcus was not isolated in any of the infected samples. Likewise in non-infected tonsils, the most common organism isolated was again Streptococcus viridans followed by Micrococcus and Diptheroids. In these specimen no Beta haemolytic streptococci was isolated from the control group.

Conclusion: Thus, the study is able to put forward the fact that most common organism affecting the tonsils in infected as well as non- infected state is Streptococcus viridans. Where as Beta haemolytic streptococci was not found in non- infected tonsils, like wise Micrococcus was not found in infected tonsils.