While not completely ignored by administrative case law, the quality of preparatory inquiries is not considered an essential issue. However, it is important in two ways. Firstly, it is a condition for a reasonable time period before a ruling is issued, and secondly, in substance it is important as it also conditions the outcome of the dispute and contributes towards the quality of the court’s decision. On the one hand, through their ability to set out the best possible conditions for being understood by the judge and to avoid that the latter is mistaken as regards the meaning of any submissions and the scope of any grounds, the writings submitted by the parties are a vector for the proper comprehension of their arguments; and, on the other hand, through their completeness and their consistency - and thus, their relevance -, these writing are a vector for the proper execution of the adversarial procedure. Under such conditions, it can be said that the parties influence the intelligibility of the preparatory inquiry. However, they also influence the fairness of the preparatory inquiry. While the purpose of this study is not to discuss the interest that should be formally taken in the principle of fairness in the administrative process - which is now called for by a significant proportion of doctrine - it should be noted that the fair behaviour of parties is of interest to ensure the quality of the preparatory inquiry. As it cannot resolve all matters - with the parties not able to effectively fight all of the opponent’s moves - the adversarial principle is unable to overcome all obstacles alone. By acting in support of the adversarial principle, the fairness demonstrated by parties contributes towards the quality of the preparatory inquiry. Furthermore, despite the well known assertion according to which administrative procedures before the courts are inquisitorial, the judge’s action is often all too limited for the judicial “truth” to be revealed. By adopting a fair behaviour, each party contributes towards the quality of the preparatory inquiry and, as such, it can be said that the fairness demonstrated by parties complements the inquisitorial natural of the procedure. As a result of the above, we can state that, whilst variable throughout each process, the quality of writings and the quality of behaviour do offer a certain stability: as they influence its intelligibility and its fairness, the parties also influence the quality of the preparatory inquiry.