To evaluate the effect of vital tooth bleaching agent and alcohol pretreatment on dentin bonding, flat dentin windows were produced on the buccal side of the crowns of fifty-five extracted, human premolars. A bleaching gel, Opalescencewith 10% of carbamide peroxide (Ultradent Product, USA) was daily applied on the teeth of three experimental groups for six hours for 10 consecutive days, while teeth of a control group were not bleached. After 6 hours of bleaching gel application, the spec- imens were washed and stored in saline until the next day application. After application of One-step� dentin bonding agent (Bisco, USA), Z-250 � resin (3M-ESPE, USA) was bonded to dentin with a mount jig. Shear bond strength was measured with an Instron machine (Type 4202, Instron Corp., USA) after 24 hours. The results were analyzed using one-way ANOVA and Duncan' s multiple range test at p 0.05) and between delayed bonding group and un-bleached control group (p > 0.05). In the condition of the present study, it seems that alcohol pretreatment after bleaching procedure can reduce the adverse effect of vital bleaching agent on dentin bonding. (J Kor Acad Cons Dent