This dissertation presents a new analysis of theatrical improvisation, not as a theatrical practice but as a condition of the creative process; the focus is on the processes of the actor as signifier and site (producer) of a complex system of exchange. It explores the actor as creator of a macro-text that consists of the fixed element of the script and its variable interactions with the other actors and the audience. I demonstrate that improvisation is the condition that allows the actor to establish non-linear relationships between the text and the spectators through parallel subtexts that he creates ex novo. Such relationships happen in virtue of a ‘complexisation’ of the text that enriches its literal meaning. I observed the Spanish director José S. Sinisterra’s work in which he trained his actors to develop parallel subtexts in order to improve their ability to make a text complex. He argued that the actor’s expression of the text needed to provoke the spectator, through chaos and order. I then, studied the creativity process from a scientific point of view in order to understand in which way chaos and order work inside the mechanisms of performance. Thanks to the application of the chaos and complexity theory to the theatrical processes, attempted here for the first time, I consider the actor and the performance as ‘complex dynamic systems’ like a cell, a human being or life itself, in which, paradoxically, order and chaos coexist and maintain the system in balance; the continuous passages from chaos to order and vice versa, create the necessary tension and energy that put the spectator in the condition of building his own meanings. This study intends to define the fields of action of order and chaos, in both actuation and reception of text, as well as to identify fixed and variable determinant factors which could alter the components of the actor and the whole play’s system, to the and of increasing the necessary tension for complexity. Important theories on semiotic aspects of theatre and reception processes are taken in consideration like those by Iser, Eco, Ubersfeld and De Marinis as well as those by the mayor theatre directors of the Twentieth century, from Stanislavski to Mejerch’old, Kantor, Grotowski.