The emergence of evidence-based medicine has challenged many conventional ideas about medical research. Instead of focusing just on individual studies, a science of systematic reviews has evolved. The Cochrane Collaboration, still only 15 years old, aims to collate systematically all randomized controlled trials through regularly updated systematic reviews to provide the best current evidence on different therapies. The most recent update has over 3000 reviews and over 1700 more protocols registered. Many expected that methodologically rigorous systematic reviews would bring clarity and agreement on the evidence for each therapy, so at first sight the disagreements between Kaduszkiewicz et al. and Birks seem surprising.