To elucidate the characteristics of elution of base monomer from a composite resin filling including the bonding layer, elution of TEGDMA from the composite resin, the bonding agent and a combination of them were investigated.In addition, the concentration of TEGDMA permeating through the bonding agent layer of Photobond was measured.The concentration of TEGDMA eluted from the combination was greater than that from the bonding agent specimen.Although the bonding agent specimen of Photobond revealed no elution of TEGDMA, some elution of TEGDMA was found from the specimen containing a combination of Photoclearfil Bright and Photobond.TEGDMA proved to permeate through the bonding agent specimen of Photobond an there was no relationship between the thickness of the bonding layer and the permeability of TEGDMA.The new method used in this study was suggested to be useful to investigate the monomer elution from a composite resin filling including the bonding layer.