This paper presents the results of an intensive research on the phenomenon of split intransitivity in Campanian varieties. In the first part it presents the phenomenon according to the different theoretical approaches considered, in order to analyse the considerable amount of data presented in the following sections. The second part is devoted to the central Campanian varieties, in which the data from the metropolitan area of Naples, Salerno and the hinterland are exposed. The peculiarity of the Acerno variety, which is more isolated than the others, leads to present the data of this variety separately. The last part presents the data from the south of the region, the Cilento, divided into two different areas, which are very different from a sociolinguistic point of view. For each dialectal area, an attempt is made to identify the internal parameters that characterise the variation in the choice of the auxiliary and, where necessary, the authors recourse to sociolinguistic variation or contact among different varieties that may have had an influence on the phenomenon.