Since a few decades, policy evaluation is a main topic in Western democracies. It identifies, measures and appreciates effects, outcomes and impacts of a policy. Yet, there is not a common way to institutionalise that policy instrument; one can observe many differences in terms of its intensity and maturity, as well as a diversity of institutional device. Compared to other countries, Belgium is characterized by a low visibility and weak decisional impact of evaluation. Public demand for enlightening state action rarely takes the form of a demand for evaluation. The word 'Evaluation' is frequently pronounced, but most often in a political sense. In this article three types of arguments can be put forward to explain this Jack of evaluation: a lacking commitment of Parliament and political staff, the fragmentation and weak autonomy of the civil service and the domination of political parties upon the Belgian political and administrative system.