Abstract: In clinical practice many herbal preparations have been using in the management of Tonsillitis (Thundikeri). Thrikatu kalinga katuka is a famous decoction prescribed only by some of the renowned physicians according to their experience. Its efficacy against Streptococcus pyogenes is not proved by laboratory investigations up to now. This study was carried out to determine the antibacterial effect of the above decoction against the laboratory specimen of S. pyogenes and to determine the most effective concentration against the organism.