Objectives:Ipochlorite of Sodium and EDTA are an integral part of endodontic treatment. This agent can effect on the dentin surface after cavity preparation. The effects of these substances might have on the shear bond strength of dentin bonding systems has not yet been determined.Methods: The purpose of this study was to evaluate the micro-shear bond strength to human dentin of one commercially available resin bonding systems on dentine treats by NaOCl and EDTA. Sixty freshly extracted first molars were included and divided in two groups.One group was treated (TG) alternatively for 15 minutes by NaOCl 5.25% and 5 minutes by EDTA.The remain group(UG) was the control without any treatment. Shear bond strengths to dentin were determined according to ISO TS 1140550,1994.The adhesive,Optibond Solo Plus(Kerrhawe)(DBS), was applied on dentin surfaces following manufacturers directions and light cured. 3.5 x 2.0mm cylindrical Point four (Kerrhawe)composite cylinders were sheared off (Zwick universal-testing-machine, 1mm/min) after thermocycling (5-55°C, 5000x). Pairwise comparisons among groups were made using the Mann-Whitney-U-test (p < 0.05). Median values and 25- and 75% quartiles were then calculated;Results: The result of treated group(TG) was the following 20.0 (12.9/26.0) while UG showed 34.5 (16.3/39.7).Conclusions: The specimes treated by NaOCl and EDTA provided lower values in dentin compared to the control group.Treatment by NaOCL alternatively with EDTA on dentin surface decrease the bond strength of DBS.