Evil is a concept traditionally alien to psychoanalytic discourse. Using a Kleinian framework it is argued that the term ‘evil states of mind’ usefully describes the experience of possession by a destructive personality suborganization founded on identification with a bad internal object. These states may be temporary and give rise to guilt and concern. In some cases, however, benevolent parts of the self are attacked and obliterated. The resulting loss is not experienced and mourned; instead perverse logic transforms it into a triumph. In this way the pain of loss and envy of the good possessed by others is denied, and psychic truth is replaced by perverse thinking in which good and bad are reversed. Satanic cults represent the pure organizational embodiment of the destructive subpersonality. Variants of evil states of mind are described with reference to psychotherapy patients and interviews with satanic cult members.