The material published here is the result of work begun in the summer of 1930 in collaboration with Freud. The starting point was a case of delusional jealousy which I had previously analyzed and published and which inadvertently had revealed a wealth of unsuspected information concerning a period hitherto unknown, antedating the Oedipus complex and consequently termed preoedipal. The written record of this collaboration is a manuscript which consists of my notes, typed after discussions with Freud, and Freud's own marginal comments, ideas and suggestions.