We have isolated cells from the interface membrane between bone and implant to identify which cell was playing a role in the bone resorption. The interface membrane was made up of three layers of which foreign bodies and granulomas were identified and the foreign bodies were confirmed mostly to be the polyethylene by the polarized microsope. The morphology of the cultivated cells were variable; mononuclear cells were spindle or polygonal shape and giant cells were also identified. The giant cells were positive to TRAP reaction and negative to immunocytochemistry to CDllb and CD14 which shows same phenotype expression with osteoclasts. And they could make resorption pits on calcified bone slices. We have confirmed the bone resorption activity of the giant cells of interface membrane of which activity would persist as long as they exist, so adequate implant material and operative techniques are needed to eliminate these bone-implant interface membrane.