Abstract: Trichloracetic-acid (TCA) was introduced as an adjunct material capable of eliminating bleeding and cervical fluid especially in cervical restoration placement. The aim of this study was to evaluate the effect of 30 and 50% trichloracetic-acid as an etching agent on bond strength of composite-resin to enamel and dentin. Seventy-two intact human molar teeth were divided into 6 equal groups randomly. In the first 3 groups smooth enamel surfaces were prepared in buccal surfaces. In the remaining 3 groups the occlusal surface was reduced so that superficial dentine was exposed. Then, surface treatment was performed by different materials as follows: groups 1 and 4 by 37% phosphoric acid; groups 2 and 5 by 35% trichloracetic-acid and groups 3 and 6 by 50% trichloracetic-acid. Then Single Bond (3M ESPE) was applied and composite-resin cylinder (Z100, 3M ESPE) was cured. The samples were incubated in distilled water at 37�C for 24 h and composite cylinders were applied under shear force. The data was analyzed by ANOVA. Mean fracture strengths in the study groups ordered from 1-6 were: 19.91�9.02, 18.43�5.69, 19.05�5.48, 10.83�7.22, 10.04�5.57 and 9.48�1.97. There were no significant differences in bond strength of composite-resin using 37% phosphoric acid, 35 or 50% trichloracetic-acid to neither enamel nor dentine (p>0.05). TCA could etch enamel and dentin similar to phosphoric-acid. Trichloracetic-acid application as an enamel and dentine etchant especially in cervical restorations, where it can act both as an etchant and an astringent or gingival fluid reducer, needs to be more investigated.