Abstract: The invention relates to a process and an apparatus for manufacturing plastic pipes having a composite structure by extrusion.The material forming the inner and outer walls of the tube is introduced into a special heated and regulated distribution head and is separated into two distinct streams between which a filling material forming a first stream is injected. These three streams are brought together and placed in contact, thus forming a blank which is given its final dimensions by being passed into a conventional tool comprising a trefoil, die and mandrel, followed by a conformator.Application to the manufacture of large dimension tubes for the disposal and drainage of sewage and rainwater.