As far as Italy is concerned, several collections of sermons of the IVth and Vth centuries have been kept. Among them, the sermons of Zeno of Verona, Gaudentius of Brescia, Chromatius of Aquileia, Maximus of Turin, Peter Chrysologus (for Ambrose of Milan, Explanationes in XII palmos and De sacramentis are concerned) provide a consistent and coherent set of a geographically and culturally bounded area. The paper shall consider the role of sermons over the period from the 360s to the 450s in Northern Italy in a twofold perspective. It is actually about understanding the extent to which preaching, as a major driver of faith, served as a means of unifying and spreading the ecclesia. It is also about analyzing how preaching was also used to categorize individuals according to their degree of spiritual advancement by creating some boundaries inside the community. Becoming Christian in Late Antiquity implied to follow a spiritual progression which could be enlighted by the study of preaching. As rallying as splitting point, the sermon established the place of the faithful in Church. From a liturgical point of view, I will focus then on the lectures that were marked out for some of these status, especially catechumeni, competentes, neophyti (for example, the lifes of the Patriarchs were read to the competentes in Milan), and on the exegetical discourse, spiritual or moral, that was related to these lectures. Such an analysis on sermons must also include a sociological approach. Therefore, it will highlight the variety and composition of audiences: was it really a selection that came to worship (MacMullen 1989) ? Did that make a difference preaching in a small town or in an imperial capital ? Finally, the interactions between preachers and audiences (adresses, questions etc.) will be analyzed from a pastoral point view. The whole approach should help to understand how the process of becoming Christian was anchored in a pedagogy of faith.