A general survey of the borderline literature is presented. The diagnostic label "borderline" has predominantly been used in North America; nevertheless, many roots of this conception originate in the classical European psychiatry and psychoanalysis. The various diagnostic (mainly descriptive) criteria and characteristics of the borderline are discussed, as well as the most important psychoanalytic hypotheses and conceptions (such as splitting, projective identification, identity diffusion). The therapeutic principles are mentioned as well. The analysis of the surveyed literature reveals on the one hand, that a well defined borderline exists neither as a generally acknowledged clinical entity nor as a circumscribed psychopathological syndrome. On the other hand, there are three various borderline concepts clearly discernible: 1) borderline conceptualized as a form of schizophrenia, 2) borderline conceptualized as synonymous with the general category of psychopathy (personality disorder) and 3) borderline conceptualized as a special form of psychopathy.