Jealousy is a very complex 'feeling-state' which has many origins. Those that are rooted in the Oedipuscomplex were described by Freud, Fenichel, Jones and others. In this paper the author tries to show that jealousy may have a much earlier origin, which is situated in the separation-individuation phase. Problems with self-objects (Kohut) may result in a situation in which in later life partners are still seen as selfobjects that have the function to maintain self-esteem and self-cohesion. Their failure in achieving this will give rise to narcissistic rage, threatening the existence of the needed selfobject, thus leading to an intolerable conflict. Jealousy, in its imaginary form, has the function to mitigate the agression by introducing an imaginary third person. This can be seen as a reenactment of the situation with real third persons in infancy, who were envied by the child. The agression is now directed towards the third person in an effort to resolve the ambivalent conflict with the partner. Jealousy can thus be seen as a defense-mechanism, which often fails as is evident in cases of 'crime passionel'.