Ex ante research can contribute to evidence-informed policies. In this article, we explore numbers and types of ex ante studies as well as their use. First, we took stock of a potentially wide range of ex ante studies published by the Dutch government between 2005 and 2011, applying a systematic approach. Though unevenly distributed across ministries, quite a number and variety of studies were found covering among others: feasibility, intended effects and side effects. Subsequently, we looked into five cases to explore how ex ante studies were used and why. We tentatively conclude that the political decision-making context is key.