Cochrane Review Groups (CRGs) are responsible for providing review authors with references to studies that are possibly relevant to their review. The majority of CRGs employ a dedicated Trials Search Co-ordinator to provide this service (see Section The information in this chapter is designed to assist authors wishing to undertake supplementary searches for studies and to provide background information so that they can better understand the search process. In all cases review authors should contact the Trials Search Co-ordinator of their CRG before starting to search, in order to find out the level of support they provide.


This chapter will also be useful to Trials Search Co-ordinators who are new to their post, as well those who are more experienced, who may wish to consult this chapter as a reference source.


This chapter outlines some general issues in searching for studies; describes the main sources of potential studies; and discusses how to plan the search process, design and carry out search strategies, manage references found during the search process and correctly document and report the search process.


This chapter concentrates on searching for randomized trials. Many of the search principles discussed, however, will also apply to other study designs discussed elsewhere. For some review topics, for example complex interventions, it may be necessary to adopt other approaches and to include studies other than randomized trials. Review authors are recommended to seek specific guidance from their CRG and refer also to the relevant chapters of this Handbook, such as Chapter 13 for non-randomized studies, Chapter 14 for adverse effects, Chapter 15 for economics data, Chapter 17 for patient-reported outcomes, Chapter 20 for qualitative research and Chapter 21 for reviews in health promotion and public health. Review authors searching for studies for inclusion in Cochrane reviews of diagnostic test accuracy should refer to the Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy.


The numerous web sites listed in this chapter were checked in June 2008.