In this work, we discuss the role that the institutionalization of systems for evaluating public programs and policies can play, in the creation or improvement of accountability mechanisms in public management. More specifically, we propose to analyze the relationships between the strengthening of the government's evaluative function and capacity and the promotion of increasing levels of publicizing of information and the creation of mechanisms of accountability. Analyzing the cases of the Sistema de Avaliação de Rendimento Escolar do Estado de São Paulo - SARESP (System for Evaluating School Performance in the State of São Paulo) and the monitoring and evaluation system of the Programa Estadual de DST/AIDS - PE-DST/AIDS (the State SDT/AIDS Program), we venture a hypothesis for the different levels of accountability provided by these evaluation mechanisms, namely, that the different levels of transparency and responsibility afforded by the evaluation systems and mechanisms appear to be more directly related, in terms of their management, to the institutional design in which the policy or governmental program is inserted, and with the stakeholders, than to the intrinsic characteristics of the studies or systems for evaluating public policies.