Objectives: For adhesive root canal obturation dentin bonding agents with antimicrobial activity may be clinically advantageous. Therefore, the antimicrobial activity of a dentin bonding agent with an antibacterial substance (MDPB) was compared with two root canal disinfectants on two endodontically relevant strains, Enterococcus faecalis (Ef) and Candida albicans (Ca). Methods: 17 µl of the test substances (Clearfil Protect: Primer and Bond, Kuraray; ChKM-solution, Haupt; and ED84, Speiko) were pipetted on a filter disc and placed on blood agar plates which had been inoculated with Ef (ATCC 29121) or Ca (ATCC 10231). The calcium hydroxide preparation (Calxyl) was transferred on the filter disc (6 µg/filter) and then immediately placed on the plates. 0.2% Chlorhexidine solution was used for control on each plate. After incubation (24 h, 34°C, no CO2) the growth inhibition zones were evaluated by measuring the distance between the margins of the filter disc and the inhibition zone. For each strain and each substance 10 samples were tested. Medians and 25/75% percentiles were calculated and Mann-Whitney-Test was performed for statistical analysis. Results: Chlorhexidine evoked 4.3 mm (Ef) and 4.5 mm (Ca) zones. Clearfil Primer produced inhibition zones of 2.4 mm (Ef) and 6.3 mm (Ca). ChKM was significantly more effective in both Ef (5.0 mm) and Ca (16.5 mm) than all other test substances. ED 84 was less effective on Ef (2.0 mm) than the Clearfil Primer, but slightly more effective on Ca (9.5 mm), both being statistically significant. The calcium hydroxide preparation and the Clearfil Bond were not effective on both strains. Conclusions: Clearfil Protect Primer having antimicrobial activities against endodontically relevant strains similar to those of classical root canal disinfectants could be considered of being used within adhesive root canal obturation techniques.