The practice of ex post evaluation combined with those of ex ante and in itinere are essential tools for steering public investments. The challenge is both to stimulate citizen debate on a well-argued basis and to allocate state resources efficiently. With the 2012 law on the prior evaluation of public investments, the Programme d’Investissement d’Avenir, which systematizes ex post evaluation, and the Grand Plan d’Investissement, which is based on in itinere evaluation, the State has equipped itself with steering tools in recent years. However, there is still some room for improvements because there are still misunderstandings about the supposed constraints of evaluation and its real objectives.