The purpose of this study is to determine the antibacterial effect of Dilute Formocresol and Eugenol and Propylene glycol. The experimental drugs are Formocresol in Propylene glycol (5, 10, 20%) and Eugenol in Propylene glycol (50, 75, 100%) and Propylene glycol. The organisms selected for study were Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus subtilis which are found in infected root canals and are highly resistant to antiseptics. Isolated bacteria were inoculated on blood agar plate and the plates were incubated at $37^{circ}C$ for 18 hours and the zones of inhibition then measured. The results were as follows ; 1. The antibacterial action of Formocresol was effective even at 5-10 percent and the action increased when higher concentration was used. 2. The antibacterial action of Eugenol was not effective and the action decreased when higher concentration was used. 3. Propylene glycol itself possessed some antibacterial properties and showed that the antibacterial action of Propylene glycol might be almost the same as that of Eugenol. 4. Among the experimental organisms, Pseudomonas aeruginosa was found to be the most resistant to all the experimental drugs.