"I want to be free to pursue other opportunities," he said. Mr. Bess added that he'll leave the agency after a transitional period to allow time to update clients.
An agency spokeswoman said the agency will transition Mr. Bess' duties through the fall.
Mr. Bess had been chairman-CEO of Young & Rubicam's Y&R Advertising, New York, the network's flagship office, since 2001 before taking his current post. He was succeeded in March by Michael Patti, who is also chief creative officer.
In May, Michael Dolan, chairman-CEO of Young & Rubicam resigned, and Ann Fudge, a divisional president at Kraft Foods, replaced him.
No strain with Burger King
Mr. Bess asserted that he is leaving the agency in good shape and dismissed reports that the agency's relationship with new client Burger King Corp. was in any danger.
"I'm very pleased with where we are with Burger King," he said. "I couldn't be more confident."