Control of infection from methicillin resistant Staphylococcus aureus (MRSA) has been a healthcare focus for more than 50 years. One of the reasons that active surveillance testing (AST) for MRSA is expected to be effective is that the greatest risk factor for developing clinical disease is to first become colonized in the nares with MRSA. Critically, persons who are either colonized or infected with MRSA are equally likely to have their skin and surrounding environment contaminated with this organism. Therefore, strategies to limit transmission that consider both colonized and infected persons are most likely to be successful at reducing disease. For healthcare organizations that do not have MRSA well controlled, the recent SHEA compendium recommends AST as one method to identify carriers and reduce spread to new patients. NorthShore University HealthSystem began an AST program for MRSA control on August 1, 2005 and realized a 70% reduction in clinical MRSA disease. Careful monitoring of patient benefit and cost reduction associated with lowered healthcare associated infection justifies the program to hospital administration. In 10 years the MRSA control program led to a net healthcare benefit of $20 million in reduced cost, with more than 1,000 infections avoided and 180 prevented deaths.