This is an archived version of the Handbook.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

The Cochrane Central Register of Controlled Trials (CENTRAL) serves as the most comprehensive source of reports of controlled trials. CENTRAL is published as part of The Cochrane Library and is updated quarterly. As of January 2008 (Issue 1, 2008), CENTRAL contains nearly 530,000 citations to reports of trials and other studies potentially eligible for inclusion in Cochrane reviews, of which 310,000 trial reports are from MEDLINE, 50,000 additional trial reports are from EMBASE and the remaining 170,000 are from other sources such as other databases and handsearching.


Many of the records in CENTRAL have been identified through systematic searches of MEDLINE and EMBASE, as described in Sections and CENTRAL, however, includes citations to reports of controlled trials that are not indexed in MEDLINE, EMBASE or other bibliographic databases; citations published in many languages; and citations that are available only in conference proceedings or other sources that are difficult to access (Dickersin 2002). It also includes records from trials registers and trials results registers (see Section 6.2.3).


CENTRAL is available free of charge to all CRGs through access to The Cochrane Library. The web address for The Cochrane Library is: Many health and academic institutions and organizations provide access to their members, and in many countries there is free access for the whole population (for example through funded national licences or arrangements for low-income countries). Information about access to The Cochrane Library for specific countries can be found under ‘Access to Cochrane’ at the top of The Cochrane Library home page.