Abstract: An extermination system provides for the introduction of insecticide within the wall cavities of a building to provide for effective extermination of insects nesting in and passing through the wall cavities. The system includes fittings which are installed through a panel or surface of the wall and which provide a passage to the wall cavity. The fitting passage is adapted to receive the outlet of an insecticide supply device, which can be an aerosol can, whereupon an insecticide can be injected directly into the wall space to exterminate insects within the wall space. Insecticide supply devices suitable for use with the invention are also disclosed. The invention provides an effective extermination system which will reduce the exposure of the occupants of the building to insecticide.