The Cochrane Collaboration represents a quite successful example of a grass roots international effort aimed at contributing the growing demand for valid and reliable information on the effects of health care intervention, eagerly sought by consumers, patients, doctors and policy makers worldwide. The Cochrane Collaboration is fully aware that part of its success is due to the originality of its founding principles and that the challenge ahead is to maintain its ‘Cochrane Collaboration brand’ while understanding how a mature organisation can cope with the expectations of the relevant stakeholders with whom it seeks to collaborate. In this editorial reference is made to the strategic reflections emerged from the internal review that the organisation has recently completed to guide its years ahead.

The Cochrane Database of Systematic Reviews (CDSR) evolved in response to Archie Cochrane's challenge to the medical profession to assemble “a critical summary, adapted periodically, of all . . . relevant randomized controlled trials”. CDSR has been an electronic publication from its inception and this has meant that Cochrane reviews (i) need not be constrained by lack of space; (ii) can be updated as new information becomes available and when mistakes or other ways of improving them are identified; and (iii) can be cross-linked to other, related sources of relevant information. Although CDSR has become widely cited, it must continue to evolve in the light of technological and methodological developments, and in response to the needs of people making decisions about health care.

Objectives: To describe the number of trials and participants in a typical systematic review from The Cochrane Database of Systematic Reviews.

Methods: The number of trials in 1,000 Cochrane systematic reviews in issue 1, 2001 of The Cochrane Database of Systematic Reviews was counted for three categories of trial: included trials, ongoing trials, and trials awaiting assessment for inclusion. (The term trial is used in this paper, although a small number of Cochrane reviews include studies that are not trials.) The total number of participants in included trials was extracted from a sample of reviews.

Results: A total of 9,778 trials were included in the Cochrane reviews. There were a further 356 ongoing trials and 1,138 trials awaiting assessment for inclusion. A typical review contained six included trials. Forty percent of the reviews listed ongoing trials and/or trials awaiting assessment for inclusion. Based on a sample of 258 reviews, the median number of participants per review was 945 (interquartile range, 313 to 2,511) per review and 118 (interquartile range, 60 to 241) per trial.

Conclusion: This report is a descriptive study of the number of trials and participants in a typical Cochrane review from The Cochrane Library, issue 1, 2001.

Objectives: To describe the types of report that are cited by protocols and reviews included in the Cochrane Database of Systematic Reviews.

Methods: The citation for each reference included in the Cochrane protocols and reviews published in the Cochrane Database of Systematic Reviews in issue 1, 1999 of The Cochrane Library were categorized by reference type (e.g., journal article, conference proceeding, book chapter, personal communication, Cochrane review).

Results: Of a total of 24,913 citations, 21,694 (87.1%) were references to journal articles. There was a significant difference between the proportion of references to studies that were journal articles (12,348 of 13,472; 91.7%) and the proportion of other references in this category (9,346 of 11,441; 81.7%).

Conclusion: The great majority of studies included in Cochrane reviews at the beginning of 1999 had been published as journal articles.