The effects of preliminary rulings have long been a topic of interest and, at times, of controversy among EU legal scholars. This paper purports to prove that the effects of such rulings are not truly specific and defends the use of the well-established categories of res judicata and precedent in order to describe them. Res judicata, and the idea of its 'positive' effects developed for example in the French procedural system, applies to such rulings and provides perfectly well-suited tools to describe the effects they produce within the national proceedings which give rise to them. Conversely, the concept of precedent and the analytical tools constructed for stare decisis are pertinent to describe the normative impact such rulings may produce beyond the case at hand. Both types of effects are present in preliminary rulings as in other judgments of the EU Courts.