The Brazilian health system began in the first half of the twentieth century in a structured model directly linked to the pension system.Over time, this model has undergone extensions and incremental adjustments.However, in the late twentieth century, has undergone a structural change.It was transformed into a public service as a citizenship right to be guaranteed by the state, so universal and free.The National Constituent Assembly (1987/88) can be considered a crucial moment of decision for this reform.So this becomes the key point for the analysis of paradigm shift in health policy.This paper examines the transformation of the Brazilian health system -a model of the contribution base for a universal free -with reference to analytic influence of institutionsunderstood here as rules of decision-making, government institutions and previous policies.