After acrylic injections into the vessels and mandibular block anaesthesia the pterygo-mandibular space is studied in 38 anatomical pieces. 538 colour slides have been obtained from anatomical cuts at low temperature with the scannigraph system. The results point out that a cranio-pharyngo-mandibular space is clearly distinguished laterally, from a medial maxillo-pharyngeal space. There is no transversal communication between them. On the contrary, the cranio-pharyngo-mandibular space communicates, forward and upward, with the temporal space; forward and downward, with the sub-mandibular space. The cranio-pharyngo-mandibular space contains an interpterygoid space communicating with the oval foramen by a "chimney" largely filled by the emissary pterygoid veins. A pericondilar plexus of veins is also observed. The cranio-pharyngo-mandibular space is characterised by the cellulo-adipose tissue by which it is filled and which guides the diffusion of injected solutions to the oval foramen.