OBJECTIVE To evaluate the effect of sodium hypochlorite pretreatment on adhesion to normal and caries-affected dentin using self-etch adhesives. METHODS Forty extracted human molars with coronal carious lesions were used in this experiment. The occlusal dentin surfaces including the caries-affected dentin in each group were treated as follows: group 1, rinsed with water; group 2, treated with 6% NaOCl for 15s; group 3, treated with 6% NaOCl for 30 s; group 4, application with Accel for 30 s after NaOCl-30 s pretreatment. After rinsing with water and air-drying, the treated dentin surfaces were applied with self-etch systems (Bond Force and Clearfil Protect Bond) according to the manufacturers' instructions, and built-up with resin composite. After 37 degrees C water storage for 24 h, the bonded normal or caries-affected dentin areas were isolated to create an hourglass configuration with a cross-sectional area of approximately 1 mm(2). The specimens were subjected to tensile stress at a cross-head speed of 1.0 mm/min. RESULTS NaOCl-15 s pretreatment significantly improved the muTBS of both self-etch adhesives to caries-affected dentin, while the 30 s pretreatment did not affect them. For normal dentin, NaOCl-30 s pretreatment significantly reduced the muTBS of both self-etch adhesives although the 15s pretreatment did not alter them. Furthermore, the application of Accel with a reducing effect increased the muTBS to normal and caries-affected dentin treated with NaOCl for 30 s. CONCLUSIONS The effects of NaOCl pretreatment on bonding of both self-etch adhesives were dependent upon type of dentin (normal and caries-affected dentin) and the treatment time.