Owing to many prosopographical studies, it is possible to value the situation of the praetorian prefects in the end of the Principate, particularly at the severan period, that is also the zenith of the Roman jurisprudence. Two tendencies emerge from the prefect’s career. From the middle of the second century, and in particular under the Severans, the praetorian prefecture points out the acme of the equestrian career, whose regular steps, military and above all cilvil, are henceforth organised and ended with the access to the different equestrian prefectures. These prefects are with the superior clarissimi officials the ruling circle composed with men with a long experience and faithful to the emperor. On the other hand, since the reign of Antoninus Pius, the praetorian prefecture reflects the predominance of a restricted circle, the circle of the jurists who are the imperial secretaries, and a few of them reached equestrian prefectures, among them the praetorian one. The importance of this circle of jurists is attested by the competences of these prefects : to the original military function they have added wider judicial competences and their contribution to the making of imperial constitutions, to which they refer and that they annotate in their books and in which emerge in particular two spheres relating to the public authority, fiscal law and military law. Being in a position of trust and ability, they are servants of an imperial rule which has become an administrative monarchy.