Purpose: This study was designed to compare the self-etching with the etch-and-rinse adhesives regarding the degree of conversion and antimicrobial activity against cariogenic bacteria. Materials and Methods: The materials used were AdheSE (two-step self-etching), Adper Prompt L-Pop (self-etching, single-step) and Excite (etch-and-rinse) adhesives. The degree of conversion was measured using Fourier Transformation Infrared Spectroscopy. The absorbance peaks of infrared rays by the aliphatic C=C was detected at 1632 to 1637cm-1 and the aromatic C=C peak at 1610 to 1500 cm-1.The antimicrobial activity was evaluated using the microorganisms Streptococcus mutans, Lactobacillus salivarius, and Actinomyces odontolyticus, with a disk diffusion method. Chlorhexidine digluconate solution 0.2% was used as a positive control. Zones of inhibited bacterial growth were observed and measured. Results: AdheSE showed the highest degree of conversion, followed by Excite, while Adper Prompt L-Pop had the lowest values. A significant difference in the degree of conversion was found between Excite and Adper Prompt L-Pop as well as AdheSE and Adper Prompt L-Pop. On the other hand, there was no significant difference between Excite and AdheSE. Adper Prompt L-Pop showed an antimicrobial effect against Streptococcus mutans and Actinomyces odontolyticus while it was unable to inhibit the growth of Lactobacillus salivarius. AdheSE could inhibit the growth of Streptococcus mutans only. Excite did not produce inhibition zones to the tested microorganisms. Conclusion: Adper Prompt L-Pop showed the worst degree of conversion. AdheSE and Excite had the highest degree of conversion. Appreciable antimicrobial activity was noted with self-etching adhesives, while the etch-and-rinse demonstrated no antimicrobial action. Keywords: etch-and-rinse, self-etching, degree of conversion, antimicrobial action, two-step adhesive, single-step adhesive