The Cochrane Collaboration is an international not-for-profit organization network of scientists, clinicians, consumers and other decision-makers dedicated to conducting systematic reviews of interventions related to prevention, treatment and diagnosis. The Collaboration also includes methodology working groups. Cochrane Reviews are performed according to a rigorous set of standards, and undergo formal peer-review. In this presentation, the Cochrane standards will be presented, along with alternative approaches that have been advocated in published guidelines. The focus will be on questions of validity, and whether a single standard for the conduct of systematic reviews is appropriate.