Background: The Cochrane Collaboration has a long history of consumer involvement with consumers involved in its democratic processes since the beginning of the organisation. However over the past seventeen years considerable variability in the practices and support for consumer involvement has emerged across the Collaboration. There has been relatively little study of consumer involvement in the organisation. Most information about consumer involvement comes from selected case studies and surveys with low response rates. Objectives: This study sought to find out how consumers are involved in The Cochrane Collaboration. Methods: The study used an action research approach with the entity modules on the Cochrane Library as a primary source of data to determine how consumer involvement is described and understood across the whole of the Collaboration. The availability of an entire cohort of entity modules compensated for data limitations. Entity modules were examined to determine what different entities believe important to communicate to others. These data were supplemented by interviews, reports and data sources. Theoretical conceptualisations of consumer descriptions and roles were verified by presentation to key stakeholders for feedback. Results: Three overlapping groups of consumers operating in the Collaboration were identified: consumer volunteers; consumer facilitators; and consumer organisations. Consumer tasks can be categorised into three main areas: involvement in decision-making; involvement in the preparation of reviews; and involvement in promotion and dissemination. The majority of consumers in the Collaboration are involved directly with review groups and are not associated with the Consumer Network. Conclusions: The findings suggest that new strategies are needed to support consumers who want to be involved in the Collaboration but further progress on supporting consumer involvement will be determined by how future consumer involvement will be funded as this will determine the types of strategies that can be employed and how they will be implemented.