As with the two preceding guidelines of this series, these practice guidelines for the pharmacological maintenance treatment of bipolar disorder were developed by an international task force of the World Federation of Societies of Biological Psychiatry (WFSBP). Their purpose is to supply a systematic overview of all scientific evidence relating to maintenance treatment. The data used for these guidelines were extracted from a MEDLINE and EMBASE search, from recent proceedings from key conferences and various national and international treatment guidelines. The scientific justification of support for particular treatments was categorised into four levels of evidence (A-D). As these guidelines are intended for clinical use, the scientific evidence was not only graded, but also reviewed by the experts of the task force to ensure practicality.