Endeavor and the William Morris Agency agreed Monday afternoon to a merger that dramatically redraws the map for Hollywood's talent agencies.

WMA's 20-person board and Endeavor's 28 partners, in separate meetings, approved the deal, the largest combination of two existing agencies in Hollywood history. While things will not be finalized for several weeks as regulatory approvals are sought, the stage already is set for fresh upheaval as rival agencies attempt to lure agents and clients away from the new combine.

The new agency will operate under the moniker William Morris Endeavor (WME) Entertainment, preserving the venerable William Morris name that has become synonymous with repping talent while giving Endeavor room in the spotlight. And it will position itself as a challenger to dominant industry agency CAA. WMA's Jim Wiatt will serve as chairman of the new agency, with Endeavor's Ariel Emanuel and Patrick Whitesell and WMA's David Wirtschafter all serving as co-CEOs.

WME's new board will consist of Wiatt, Emanuel and Wirtschafter along with John Fogelman, Peter Grosslight and Jennifer Rudolph Walsh from the WMA side and Rick Rosen and Adam Venit from Endeavor. For those keeping score, that's four from Endeavor, five from WMA.

The merged agency, uniting WMA (founded in 1898) and the upstart, 14-year-old Endeavor, will recharge WMA's film and TV departments by bringing in a wealth of talent repped by Endeavor. It also will open the doors for the Endeavor side to have a stronger presence in music, publishing and corporate representation, areas that are WMA's strengths.

The new agency is expected to pull in more than $300 million in annual revenue.

At the moment, WMA houses about 300 agents, and Endeavor has 80. The new agency is expected to shed about 100 agents, many of which will come from the WMA ranks, which could only heighten a wrenching period of assimilation as the companies blend their disparate cultures.

In the process, a number of prominent names on both sides are expected to depart.

On the Endeavor side, motion picture agent Tom Strickler, one of that firm's founding partners, announced his resignation Monday morning. At WMA, motion picture agent David Lonner, who moved from Endeavor to WMA in 2003, also is leaving but has not announced his plans.

In an e-mail message to his co-workers, Strickler, who is stepping away from the talent business, said that he would be "taking some time off and heading to distant shores and points unknown." Although he decided against moving to the new company, he took a moment to praise Endeavor's "can-do spirit ... commitment to the best and ... common decency" and said he'd be rooting for its success from the sidelines.

Lonner, whose clients include "Star Trek" director and "Lost" creator J.J. Abrams, could become a manager or move to another agency. Abrams, who is co-repped by Fogelman, is expected to stay at WMA, but other Lonner clients could follow Lonner out the door once he firms up his plans.

For rival agencies, the official word of a merger intensified what has been a frenetic few weeks of combing through agent lists and making discreet calls to their clients.

"It's the Wild West, that's the only thing I can compare it to," said one agent not at either company. "You're basically trying to figure out which agent is leaving, and then you try to decide who on their list might be most vulnerable."

The period of uncertainty - it could be as long as two or three weeks before all WMA and Endeavor agents know their fate - introduces a double-edged sword. It allows agents a grace period to reassure nervous clients, but it also provides a window for other agencies including CAA, UTA and ICM and shops such as Paradigm, APA and Gersh to make their move.

For some clients, it might be a question of immediate self-interest. If a client has a project he is hoping will get sold or greenlighted imminently, he might opt to stay with his current agent, however uncertainn that agent's fate.

If another client doesn't have anything pressing, several agents said, that client might be more susceptible to a poaching, especially if the agent might be segueing from an agency to a management job.

Regardless, agents throughout town are seeking to take advantage of the uncertainly a moment like this brings to reach out to create or build a relationship with a client repped by another shop - which, if nothing else, could be a boost for the bar and restaurant business.

"People want to hear from other people around town now," one agent said. "They need to hear they're loved."

Nellie Andreeva in Los Angeles and Steven Zeitchik in New York contributed to this report.