In this study the efficacy of the primer on adhesion of MMA (TBB-O) resin to dentin was investigated. The primer consists of two parts. One is 6% MTYA and 70% HEMA aqueous solution, and the other is 2% glutaraldehyde aqueous solution. As an etching agents, 10% citric acid-3% FeCl3 (10-3), 40% phosphoric acid, 10% citric acid, and 0.5 M EDTA were used. After etching, the two parts of the primer were mixed well and applied on the etched surface. Then MMA (TBB-O) resin or p-MBA/MMA (TBB-O) resin was applied on the treated surface. The tensile bond strengths after storage in 37 degrees C water were measured. It revealed that the primer treatment increased the bond strength despite the kind of etching agents. Though the thickness of the resin reinforced dentin was the same as that of demineralized dentin, it was not proportional to the bond strength. Then the durability of the adhesion to dentin treated with primer was examined by the thermal cycling tests. After 2000 thermocycles between 5 degrees C and 55 degrees C, the decrease in the bond strength was very small.