In the current information age, research synthesis is a particularly useful tool for keeping track of scientific research and making sense of the large volumes of frequently conflicting data derived from primary studies. The Cochrane Collaboration is a global initiative "to help people make well-informed decisions about health care by preparing, maintaining and promoting the accessibility of systematic reviews of the effects of healthcare interventions". In this paper we set the work of the Cochrane Collaboration in historical perspective, explain what a Cochrane review is, and describe initiatives for promoting worldwide dissemination of synthesized information. We also consider emerging evidence of the Cochrane Collaboration's impact on health-care practice, policy, research and education. Finally, we highlight the need for increased investment in the preparation and maintenance of Cochrane reviews, particularly those that address health issues that are relevant to people living in low- and middle-income countries.