There are currently installed in Australia eight satellite ground terminals that operate either as integral parts of or in connection with the US Defence Satellite Communications System (DSCS). One of these is at North West Cape, Western Australia; two are at Nurrungar, South Australia; two are at Pine Gap, Northern Territory; one is at the Weapons Research Establishment (WRE), Salisbury, South Australia; and two are at Watsonia Barracks in Melbourne. Despite the critical importance of this satellite system to US global military and intelligence operations, and the fact that Australian involvement in the system began more than two decades ago, there remains in Australia no public description of this system nor any discussion of the implications of Australia's involvement in it for various aspects of Australia's national security. This monograph describes the US Defence Satellite Communications System (DSCS) and its various missions and discusses Australia's role in the system. It concludes that Australia has had insufficient control over the DSCS deployments and operations in this country; that the Australian Government has been remiss in informing the public about the extent of Australia's role in the DSCS system and the implications of this involvement; and that Australia should take advantage of the DSCS facilities to support our own defence communication requirements.