This thesis studies the role of the signifier in interpretations and constructions in psychoanalytical treatments, taking into consideration the analysis of fragments of clinical cases from psychoanalysts like Freud, Lacan and Jean Allouch, among others. This work is based on the way language was taken by Freud and later by Lacan in the formulation of the concept of the unconscious. In Lacan s Retour à Freud he tries to put psychoanalysis back on track, the language path, by rereading the texts he considers canonical about the interpretation of dreams, parapraxis and wits. To accomplish this study, I followed Lacan s steps through linguistics with Saussure, Jakobson, Benveniste, Damourette, Pichon and other linguists and grammarians that were important to his psychoanalytical formulations. In order to understand Freud read by Lacan, which determined his reformulations on psychoanalysis, specifically in regards to treatment, I took into account texts in which Lacan begins to discuss speech, in the field of language, focused on the transmission of psychoanalysis and on the opposition between two existing conceptions of the treatment and the formation of the psychoanalyst. In his last seminars, Lacan ends up deciding to leave linguistics to the linguists and to coin the term linguistery to state which language psychoanalysis deals with. Based on fragments of clinical cases, I reflected on the relevance of certain signifiers that appear on the course of different treatments in which the analysts intervention enabled the analysand to abandon a previously fixed meaning and undertake a new way to the construction of his phantasy up to its crossing. Some of the signifiers used by Freud (Wortfuge-Worfugen- Wortfügung, Wortklang, Entstellung, Konstruktion, Phantasieren, among others) helped me understand the psychoanalytical technics through Freud s interpretations of dreams, wits, parapraxis and move on to lacanian elaborations on psychoanalytical treatment, interpretation, analytical act.