Although a small number of infections in total joint replacements are blood borne from distant sources, most infections appear to have been derived at operation. Strenuous attempts to reduce this risk by cleaning the air in the wound environment, coupled with prophylactic antibiotics, have reduced infection rates by an order of magnitude in a decade. During that time the potential for exchange arthroplasty in established infection has been shown, and the results are encouraging. Rigorous infection control is the key to containing this difficult and expensive problem.