The goal of this dissertation is to analyse the existing relationship between the art work, the artist and the spectator within the context of Lygia Clark s e Hélio Oiticica s work. These two artists were chosen as the object of this study because both were committed to proposing new issues regarding the inclusion of the spectator as a direct agent in the modification and even creation of the art work. They stood out in the artistic world by proposing innovating issues, searching to occupy the real space and free themselves from the bidimensionality of the canvas and the easel. The research is based on the premise that both are current references in the history of Brazilian art and investigates the span of their trajectory, from their participation in the Neoconcrete group up to their last pieces, stressing the problematics involved in each one s work and, specially, to what point they were able to establish a direct dialogue with the public.