This study investigates the presence of ambivalence as a strategy of cultural politics from modern to contemporary art in Brazil. It focuses on the development of modern art leading to the work of Hélio Oiticica, whose approach to avant-garde practice in Brazil was concurrent with intense articulations between the forces of social change and re-evaluations of the legacy of Modernism. The thesis has a strong historiographical emphasis and is organised in three parts: Part one attempts to view the emergence of Modernism in Brazil beyond the prevailing interpretations that emphasise its inadequacy compared to canonical paradigms. Part two discusses the development of abstraction in Brazil, particularly that associated with the constructivist tradition and its relationship with the prevailing positivism of a nation that saw modernity as its inevitable destiny. Such a relationship, between art and ideology, implicitly questions the purported autonomous nature of modern art. Again, what emerged were definite regional distinctions, themselves based on seemingly universal theoretical propositions. The context of Hélio Oiticica's emergence as a constructivist-oriented artist is discussed in order to establish the theoretical foundation for his subsequent articulations between notions of avant-garde and Brazilian popular culture. Part three deals with Oiticica's theoretical and artistic proposals. It centres on the artist's transition from a position concerned primarily with the aesthetic questions of art, to one in which art became engaged on a social, ethical and ultimately political level. Oiticica's relationship with concurrent developments in theatre and later in music and cinema is given particular attention. The artist's questioning of the divides between such fields of specialisation, socio-cultural borders or categories of creative production is argued to have arisen out of Oiticica's lessons from Neoconcretism as well as his individual creative approach to relations of friendship. The latter integrated the wider concept of participation that eventually drove the work through the apparent equivocation between national culture and avant-garde practice. The study concludes with an analysis of the artist's posthumous dissemination and its relation with today's contemporary Brazilian art.