Approval of new animal drugs is based on evaluation of scientific evidence provided by drug sponsors. For novel chemical entities, traditional sets of laboratory and field studies generally provide a basis for inferring post-approval safety and effectiveness. For drugs that have already been used in animal populations, such as unapproved drugs or new indications for approved drugs, there may be existing data from representative populations that are appropriate to support a regulatory decision. In the literature on evidence-based medicine, well-designed systematic reviews and meta-analyses that integrate information from population studies are considered to provide stronger evidence about treatment effects than individual randomized controlled trials. While methodologies and resources for conducting such reviews are now widely available, the use of these approaches in regulatory decision-making has some unique requirements to allow a conclusion: ‘the drug is safe’ and ‘the drug is effective’. However, systematic reviews and meta-analyses provide a rigorous framework for integrating evidence from published literature and other sources to strengthen regulatory decision-making.