These practice guidelines for the biological, mainly pharmacological treatment of bipolar depression 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 pertaining to the treatment of bipolar depression. The data used for these guidelines have been extracted from a MEDLINE and EMBASE search, and from recent proceedings of key conferences and various national and international treatment guidelines. Their scientific rigor 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 commented on by the experts of the task force to ensure practicability.