The decentralization principle is found both in the federative organization of the national State and in the basic directions of the health system in Brazil. How does it present itself in each of these dimensions and how are they connected? On the basis of an examination of this question the author analyses the Brazilian national Unitary Health System (Sistema Único de Saúde - SUS) taking account of its politico-institutional context and of its functioning. Basic categories of her analysis are interdependence and autonomy.