From today, all 18 Billetts and Xtreme offices worldwide become Ebiquity offices, including MAI in Chicago and Thomson Media Control in Germany.
Michael Greenlees, chief executive of Ebiquity, said: "Billetts and Xtreme were trusted brands in the media auditing and advertising monitoring worlds. However, we now help advertisers improve their ROI in many more ways, so we've made the decision to bring everything together under one name."
Billets was launched by John Billett in 1993 as the Billett Consultancy, part of media agency CIA. It became independent in 1995.
Billett and his management team sold Billetts in 2005 to Thomson Intermedia, which renamed itself Ebiquity in 2008 and acquired Xtreme Information in 2010.