Abstract: The duct forming sleeve assembly is used in a process for providing passageways in concrete structures for routing of pipes, cables or conduits therethrough. The assembly comprises a rectangular base plate member which is positioned within the concrete in a plane parallel to a surface of the concrete and attached to a wooden or metal floor deck, prior to pouring the concrete. The base plate has screw holes used for mounting the base plate to the deck and is provided with a plurality of cutout areas each of which is capable of accepting a cylindrical sleeve member therein. A plurality of cylindrical rigid sleeve members, equal to the number of cutout areas within the base plate are received in the cutout areas of the base plate along an axis which is perpendicular to the plane of the base plate.