The Cochrane Collaboration assesses most areas of health care. To do this, it is divided into Cochrane Review Groups (CRGs), each of which concentrates on a specific healthcare area; Fields, that draw together health care issues impacting on many CRGs (such as cancer); a Consumer Network, that represents the interests of healthcare consumers; Methods Groups develop methodological techniques; Centres with geographic and linguistic responsibilities; and a Steering Group, which provides the policy and decision-making body of the Collaboration, and this, in turn, is supported by the Secretariat.

The main work of The Cochrane Collaboration is done by about fifty Cochrane Review Groups, within which Cochrane reviews are prepared and maintained. The members of these Groups – researchers, healthcare professionals, people using the healthcare services (consumers), and others – have come together because they share an interest in generating reliable, up-to-date evidence relevant to the prevention, treatment and rehabilitation of particular health problems or groups of problems.

To become part of The Cochrane Collaboration, each Cochrance Review Group is required to prepare a plan outlining how it will contribute to the Collaboration’s objectives. This describes who will have responsibility for planning, co-ordinating, and mentoring the Group’s work (a co-ordinating editor supported by an editorial team). It also describes how the Group will identify and assemble in a specialized register as high a proportion as possible of all the studies relevant to its declared scope; and who, drawing on the studies in this register, will take responsibility for preparing and maintaining which reviews. Every Group employs a co-ordinator to organise and manage the day-to-day activities of the Group.

The science of research synthesis is still relatively young and evolving rapidly. Methods Groups have been established to develop methodology and advise the Collaboration on how the validity and precision of systematic reviews can be improved. For example, the Statistical Methods Group is assessing ways of handling different kinds of data for statistical synthesis, and the Applicability and Recommendations Methods Group is exploring important questions about drawing conclusions regarding implications for practice, based on the results of reviews.

Fields focus on dimensions of health care other than health problems, such as the setting of care (e.g. primary care), the type of consumer (e.g. children), or the type of intervention (e.g. vaccines). People associated with Fields search specialised sources for relevant studies, help to ensure that priorities and perspectives in their sphere of interest are reflected in the work of Cochrane Review Groups, compile specialised databases, co-ordinate activities with relevant agencies outside the Collaboration, and comment on systematic reviews relating to their particular area.

The Cochrane Consumer Network provides information and a forum for networking among consumers involved in the Collaboration, and a liaison point for consumer groups around the world.

The work of Cochrane Review Groups, Methods Groups, Fields, and the Consumer Network is facilitated in a variety of ways by the work of a dozen Cochrane Centres around the world (Australia, Brazil, Canada, China, Denmark, Germany, Italy, the Netherlands, South Africa, Spain, UK, and the USA). They share responsibility for helping to co-ordinate and support members of the Collaboration in areas such as training, and they promote the objectives of the Collaboration at national level. Each Centre is responsible for a number of other countries, and some Centres have branches within those countries.

The Steering Group and its several working groups are supported by a secretariat, currently based in the UK.