This is an archived version of the Handbook. For the current version, please go to or search for this chapter here.  Searching The Cochrane Central Register of Controlled Trials (CENTRAL): specific issues

CENTRAL is comprised of records from a wide range of sources (see Sections and 6.3.2 and subsections), so there is no consistency in the format or content of the records.


The 310,000 records sourced from MEDLINE are best retrieved by a combination of Medical Subject Heading (MeSH) and free-text terms. The other records, including the 50,000 records sourced from EMBASE, are best retrieved using free-text searches across all fields.


Most of the records that do not come from MEDLINE or EMBASE (about 170,000 in The Cochrane Library Issue 1, 2008) do not have abstracts or any indexing terms. To retrieve these records, which consist predominantly of titles only, it is necessary to carry out a very broad search consisting of a wide range of free-text terms, which may be considered too broad to run across the whole of CENTRAL.


It is possible to identify the records that have been sourced from MEDLINE and EMBASE by searching in CENTRAL for those records that have PubMed or EMBASE accession numbers. It is possible then to exclude these records from a broad search of CENTRAL, as illustrated in the example in Box 6.3.c.


For general information about searching, which is relevant to searching CENTRAL, see Section 6.4.