According to a trading update, third quarter revenues rose 4.9% to £1.48bn, with revenues in constant currencies up 8.1%.
In the UK, WPP has reported constant currency growth of 5%, compared with 3.7% in the first half, while Asia, Latin America, Africa and the Middle East also strengthened.
North American revenues were up 8%, compared with 8.3% in the first half. The result leaves WPP in line with the full-year target for operating margin of 15% in 2007.
The group said the recent credit crisis had not had a significant impact of levels of client spending, with "little of any effect on spending levels across the board, both functionally and geographically".
But the company added: "Any possible impact is unlikely to be reflected anyway, until the group's budgets for 2008 are finalised at the beginning of next year.
"In any event, we continue to believe that 2008 will be a good year for the industry, better than 2007."
Looking further ahead, Sir Martin Sorrell, chief executive of WPP, said he was "concerned" about the impact of the next US Presidential administration.
In an interview with The Wall Street Journal, Sorrell raised fears the advertising market is set for a slowdown in 2009 as a new administration implements strong measures to right economic imbalances early in its term.