[The Unified National Health System, 20 years: assessment and perspectives].

This article reviews the strides and challenges of the Brazilian Unified National Health System (SUS), based on an assessment of the results achieved and the constraints for effective consolidation of it objectives. The article focuses on three issues: the process of implementing the SUS, highlighting the institutional and political constraints, some of which as effects of previous policies; strides towards more accessible and comprehensive care, with an impact on some health indicators, and institutional innovations with positive impacts on the system's management; and challenges for consolidating the objectives, as a result of exogenous factors in relation to the SUS, emphasizing the need for its politicization and greater legitimization.