The purpose of this study was to evaluate the effect of collagenase and esterase on the microtensile bond in dentin bonding. After resin composites were bonded to occlusal dentin. specimens were formed and stored in PBS, collagenase, or esterase solution After 4-week storage, was determined and, the results were as follows : 1. values of Single Bond 2 were lower than those of Clearfil SE Bond for all storage medium (p0.05). 3. In Clearfil SE Bond group, esterase solution lowered bond strength more than PBS(p>0.05). Collagenase solution lowered bond strength more than esterase solution(p>0.05) and PBS(p<0.05)