Founded in 1988 in Austin, Texas, the agency has seven other US offices and one in the UK in Buckinghamshire, employing a total of 175 staff.
Public Strategies specialises in issues management, which helps companies assess public opinion and risk. Its revenues for 2005 were $38.5m with net assets at closing of $2.3m.
WPP's other PR businesses include Hill & Knowlton, Burson-Marsteller, Finsbury, Ogilvy PR Worldwide and Cohn & Wolfe.
Ealier this week, WPP Group chief Sir Martin Sorrell faced the threat of a personal criminal defamation case from Marco Benatti, the former head of WPP in Italy.
The long-running dispute involving the two men is a reversal of a decision in April, when a judge said that Benatti could not move ahead legal proceedings against Sorrell.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .