Talaka mattirai, Iti vallati meluku, tamibira parpam and Naka centuram of siddha system of medicine were screened for antibacterial activity against S. aureus, S.citreus, S.faecalis B. Subtilis, P.aeruginosa, Coli, S.Boydii, V.cholerae and Klebsiella sp. Talaka matrirai ibihibited the growth of s. faecalis, V.cholerae and B. Subtilis at a concentration of 0.6 mg/ml and 1mg/ml respectively. P.aeruginosa growth was inhibited at a concentration of 0.2mg/ml V. cholerae. at a concentration of 0.6mg/ml and S.boydii at a concentration of 1mg.l by iti vallati meluku. Tambira parpam inhibited the growth of S. faecalis and S. boydii at a concentration of 0.2mg/ml, V.cholerae at a concentration of 0.6mg/ml and S citreus and B. subtilis at a condensation of 1mg/ml there was inhibition of growth of S. citreus and B. subtilis by naka centuram at a concentration of 1mg/ml. Manometric studies revealed the total inhibition of S.boydii by Tambira parpam at a concentration of 1mg/ml while at 0.6mg/ml concentration inhibition was similar to tat of chlroamphenicol (1mg/ml). The antibacterial activity of these medicines was due to ingredients involved in these preparations.