The Cochrane Collaboration: From outside and from within

The presence of the Cochrane Collaboration (CC) has been increasing in recent years among the sources of medical information. But there is a lot of ignorance about its nature and its purposes. The main purpose of the CC - to help people make well-informed decisions about health care-is implemented by preparing, maintaining and promoting the accessibility of Systematic Reviews (SR) of the effects of healthcare interventions. Here we analyse the main features of SR and meta-analysis, their contributions and limitations. The structure and organization of the CC are described: Collaborative Review Groups, Centers all over the world, Fields, Methods groups, Consumer Network, and The Steering Group. A detailed description of the Cochrane library and of the current situation of the data base stored in it is done. Finally the impact, repercussion and future of the CC are considered, and also the challenges and improvements that the near future will probably bring.