The Cochrane Central Register of Controlled Trials (CENTRAL) is a highly concentrated source of reports of randomized controlled trial and quasi-randomised controlled trials. The majority of CENTRAL records are taken from bibliographic databases (mainly MEDLINE and Embase), but records are also derived from other published and unpublished sources. In addition to bibliographic details (author, source, year, etc.) CENTRAL records will often include an abstract (a summary of the article). They do not contain the full text of the article.
Each Cochrane Review Group maintains a collection of reports of controlled trials relevant to its own area of interest, these are called Specialised Registers. Unique content (i.e. records not already identified in MEDLINE, etc.) from these Specialised Registers is also published in CENTRAL. Groups may also collect items that are not relevant to its own field of interest; known as handsearch results, which are added to CENTRAL as well.
The overriding aim of CENTRAL is to compile a comprehensive database of reports of randomised and quasi-randomised controlled trials. For that reason records are included irrespective of language or date of publication.