Objective: The aim of the present study was to evaluate the effect of different concentrations of chlorhexidindigluconate (CHX) on microtensile bond strength (mTBS) of two dentin adhesives (Syntac Classic, Optibond All-in-One) in vitro. Methods: Seventy-two extracted third molars were included in this study. All teeth were specially prepared allowing the simulation of dentin perfusion. The specimens were randomly assigned to one of the six groups of fifteen samples each: group S-C: Syntac control group (no CHX-application); group S-0.2: immersion for five minutes in 0.2% CHX prior to bonding with Syntac, group S-5: immersion for five minutes in 5% CHX prior to bonding with Syntac, groups O-C, O-0.2 and O-5 followed the same procedure with Optibond All-in-One as adhesive. MTBS was measured 15 minutes after application of the composite (Tetric Ceram) using an universal testing machine. Results: Statistical analysis showed a significant influence of the used dentin adhesive and the pre-treatment with CHX in different concentrations (p 0.001, ANOVA). The application of 5% CHX before bonding procedure (S-5, O-5) resulted in a significant reduction of mTBS compared to the untreated control groups (S-C, O-C) (p 0.05, Tukeyxs test). Between the 0.2% CHX-groups and the controls, no significant differences could be detected (p 0.05, Tukeyxs test). Pairwise comparison between Syntac and Optibond showed no significant differences after the different pre-treatments (p 0.05, Tukeyxs test). Conclusions: Within the limitations of an in vitro investigation it can be concluded that CHX in high concentrations affected the mTBS of both tested adhesive systems. Schlagwörter: microtensile bond strength, dentin adhesives, CHX, perfused dentin