During the 2004 campaign, aimed at checking the state of conservation of the ambulatories and ancient occupation levels, it was found that earlier investigations (in the 1960s) had not compromised the possibility of finding undamaged stratigraphy. Therefore, new investigations were undertaken in two sections of the catacombs, a tunnel for public use (C) and an underground tomb belonging to a single family (A). Period I: the first phase is attested by the nuclei of burials and the first transformations of the funerary structures. A second occupation phase, which for the moment is only attested inside tunnel C, is of a later date. Tunnel C runs on a north-south alignment; two cubicula open in the west and east walls. The entrance, which has not been precisely located at present, is probably situated at the southern end of the tunnel in correspondence with the edge of the hill. The walls were occupied by at least 47 loculi, 4 arcosolium tombs housing more than one body and 13 tombs below the pavement, dug in two parallel rows. The latter are still closed by thick limestone slabs. There are at least 98 tombs relating to the first funerary phase. Moreover, inside the tunnel a layer of deliberately dumped material was identified which, covering the pavement tombs, constituted a uniform leveling of the floor above which a new series of burials were inserted. Structure A is a small hypogeum tomb belonging to a single family. This contained 7 burials each of different typology and decoration. In the first phase of its use for funerary purposes, this space, of rather irregular plan, must have been closed and accessible only from the outside. Period II and Period III: other occupation levels in the catacombs relate to the robbing of the tombs, the reuse of the hypogeum as a pseudo-dwelling and finally their abandonment and gradual filling with alluvial deposits. (Donatella Nuzzo – Paola De Santis)