“The lack of evidence of an effect associated with specific measures should not be mistaken for evidence of lack of effect” is one of the conclusions that Cooper et al (p 533) come to after a systematic review of the literature about methicillin resistant Staphylococcus aureus (MRSA).1 The infection control community has long realised that in the age of evidence based medicine and randomised controlled trials some, if not most, guidelines are based on shaky grounds. Is a method developed primarily for drug research and licensing appropriate for evaluating infection control procedures? Randomised controlled trials are useful for investigating a limited number of variables and when randomisation can be accomplished. Infection control measures are habitually complicated and depend on multiple factors. Therefore I still have some faith in the …