There were many studies to investigate the pathogenesis and prevention of infection in artificial joint replacement due to the difficulty in management of infected arthroplasty in spite of using large amounts of antibiotics. Biomaterials play a major role in the development of infection because of the way the body responds to their chemical and physical characteristics. Exopolysaccharide glycocalyx or biofilm(slime) which is produced by organisms adhered to the biomaterials has been detected and regarded as an important factor in pathogenesis. The production of slime on the biomaterials in turn makes the pathogens resistant to the antibiotics and therefore they survive. The objects of this study are to evaluate which materials are more susceptible to the adherence by Staphylococcus epidermidis, to evaluate the amount of antibiotics needed to kill the S. epidermidis adhered to the biomaterials(Polymethymethacrylate, Titanium-6Aluminum-4Vanadium alloy, Ultrahigh molecular weight polyethylene), and to evaluate the timing of administration of the antibiotics(cephradine, gentamicin) and potadine for prevention of postoperative infection. The results are as follows. 1. The materials in order of greatest adherence due to the number of organisms colonized are poly- methylmethacrylate(PMMA), ultrahigh molecular weight polyethylene(UHMWPE), and titanium alloy(Ti-6A1-4V alloy) being the least adherent. 2. With the production of biofilm the S. epidermidis becomes resistant to even that of 4 times the minimum bactericidal concentration(MBC) of antibiotics. 3. For prevention of postoperative infection, the prophylactic administration of cephradine if effective when used within 4 hours after contamination and the gentamicin and potadine are effective when used within 8 hours after the contamination with S. epidermidis.