The effectiveness of various dentin primers for adhesion of composite resin to dentin was investigated.Dentin primers composed of N-vinylpyrrolidone(NVP), methoxy polyethylene glycol monomethacrylates(M4G, M9G or M23G), or poly-N-vinylpyrrolidones(PNVP1, PNVP2 or PNVP3)were prepared.HEMA was also used as a component of the dentin primer.Fresh bovine dentin was pretreated with neutralized 0.5M EDTA or 40% Phosphoric acid and primed with each primer for 60s.Then Clearfil New Bond ^® and Clearfil FII^® were applied on the treated surface.The tensile bond strengths between composite resin and dentin were measured after 1 day immersion in 37℃ water.For EDTA pretreatment, NVP, 50% M9G and 50% M23G aqueous solution were effective in improving the resin adhesion.For phosphoric acid pretreatment, a 50% M23G, 35% HEMA and poly-N-vinylpyrrolidone aqueous solution were effective.The newly developed dentin primers MTYA・M9G(2% MTYA-50% M9G aqueous solution), MTYA・G・M9G(A:2% MTYA-50% M9G aqueous solution, B:2% glutaraldehyde aqueous solution), and MTYA・G・PNVP(A:1% MTYA-35% PNVP1 aqueous solution, B:2% glutaraldehyde aqueous solution)were effective for the dentin pretreated with EDTA.MTYA・G・PNVP gave the highest bond strength of 11MPa.