How to write a Cochrane systematic review.

The Cochrane Collaboration is a global network whose aim is to improve health-care decision making through systematic reviews of the effects of health-care interventions. Cochrane systematic reviews are published in the Cochrane Database of Systematic Reviews within The Cochrane Library ( http://www.thecochranelibrary.com), and regularly updated as new evidence arises. Cochrane Reviews are undertaken by teams of volunteer authors, who have access to free training resources, reference texts and software for preparing and maintaining their review. Here we aim to describe the steps involved to undertake a new or update an existing Cochrane Review.