The important part which behavior of this type sometimes plays in court work is witnessed to by the records of our own cases as well as those cited in the previous literature. The legal issues presented by pathological lying may be exceedingly costly. These facts make it important that the well-equipped lawyer, as well as the student of abnormal psychology, be familiar with the specific, related facts. For such students the cardinal point of recognition of this class of conduct may at once be stated to be its apparent baselessness. The only method by which good understanding may be obtained of the types of personality and mentality involved in pathological lying, accusation, and swindling, as well as of the genetics of these tendencies, is by the detailed reading of typical case histories. In this fact is found the reason for the presentation of this monograph. Appreciation of the nature of the phenomena can only be obtained through acquaintance with an entire career. Any of us may be confronted by fabrications so consistent as to leave at one or several interviews the impression of truth. Our selection of literature to summarize needs no explanation. We have simply taken all that we could find which specifically bears on the problem. Lying, in general, especially as a form of delinquency, has received attention at the hands of some authors, notably Ferriani[1] and Duprat.[2] The falsifications and phantasies of children and adolescents have been dealt with by Stanley Hall.[3] None of these goes into the important, narrower field with which we are here concerned. The foreign literature is vitally important in its opening up of the subject, but from the standpoint of modern psychopathology it does not adequately cover the ground. [1] Ferriani, Lino, ``L'Enfance criminelle.'' Milan, 1894. (Trans. Minderjahrige Verbrecher. Berlin, 1896.) [2] Duprat, G.-L., ``Le mensonge.'' Alcan, Paris, 1903. [3] Hall, G. Stanley, ``Children's Lies.'' Amer. Journal of Psychology, Jan. 1890; pp. 59-70. The fabrications, often quite clever, of the clearly insane, which in earlier literature are confounded with pathological lying, we have discriminated against as not being profitable for us to discuss here, while not denying, however, the possibility in some instances of lies coexisting with actual delusions. We well remember a patient, a brilliant conversationalist and letter writer, but an absolutely frank case of paranoia, whom we had not seen for a period during which she had concocted a new set of notions involving even her own claim to royal blood, confronting us with a merry, significant smile and the remark, ``You don't believe my new stories, do you?''