Operating as a business unit, phd USA is a part of PHD, which is a media and communications agency with more than 55 offices throughout the world. Formed in 1990, the parent company has a staff of over 2,000 professionals. It is a part of the Omnicom Media Group, which also operates the OMD and Prometheus media networks. The Omnicom Media Group is a media services division of the Omnicom Group, which is one of the leading global advertising, marketing and corporate communications companies in the world. The Omnicom Group serves nearly 5,000 clients in approximately 100 countries.