The present paper aims at exploring the possible relationships between the sexual infantile theories and the structural process that constitutes fundamental fantasy (phantasme), studying the most important freudian papers on this issue. It proposes to reflect on the specific moment in which the child is urged to construct his sexual theory, taking into consideration especifically the language effects on the organism through the presence of drives. It also advances the hypothesis of a strict determination of the infantile sexual theories by the so called originary fantasies.