The literature on lying, psychopaths, and pathological lying is reviewed in part in an attempt to consolidate and clarify the concept of pseudologia fantastica. Classifications of lying and social reactions to lies are described. The lie, consciously recognized as a falsehood and designed to produce a certain result, is distinguished from the pseudologic production, whose falsity and goal fall some place between consciousness and unconsciousness. The differentiation from delusion and memory disturbance is described. The pseudolog's story is analogous to fantasies and daydreams, and his degree of belief may lie in the halfway stage between ordinary daydreaming and the full and absolute belief of a delusion. Basic memory is structurally intact, but memories are freely and almost unconsciously invented to satisfy pressing and specific psychological needs. The factors felt by various authors to be important in the dynamic understanding of pseudologia are presented. A case presentation illustrates these factors which are seen to be (a) unresolved Oedipal conflict with severe castration anxiety, (b) successful ridicule and revenge on adults for earlier disappointments, and (c) the need to increase and maintain selfesteem.