Suicide is a major cause of death worldwide, and its impact has only been fully appreciated in the past few decades. Historically it was viewed from a religious and moral perspective, but that gave way to broad sociological and biological theories, which sometimes seemed to be mutually exclusive. There is now a wealth of knowledge which has allowed an integration of these perspectives, which have varying importance in different contexts. Part of the Oxford Psychiatry Library, this pocketbook provides a review of the diverse theories about suicide and places them in perspective - not all theories have the same weight in different settings, and there is no one management for all those who may be suicidal. However, there is now persuasive data that there are a range of suicide prevention initiatives which are effective, and that it is reasonable to expect that the suicide rate worldwide will be reduced in coming years.