Ed Zander, under pressure from Carl Icahn and others to turn Motorola around, is stepping down as chief executive. He will stay as chairman until the company's annual meeting in May.

Greg Brown, 47, the company's chief operating officer, will become C.E.O. on January 1.

Shares of Motorola were up only a little more than 1 percent on news of the management shakeup, suggesting that investors did not expect major strategic changes at Motorola or that the management change was a sign that the cell-phone business continues to struggle.

"We now wonder if today's announcement signals yet another disappointment for the handset segment and more meaningful changes that have to occur," Jim Suva, an analyst at Citigroup, wrote in a note this morning.

In an interview with Bloomberg News, Zander said he began talking to the board about stepping down earlier this year. The criticism by Icahn and other large shareholders played no role, he said.

"The one disappointment this year has been mobile devices," Zander said. "The management there had a strategy that proved not to be correct. That's been corrected. We'll be back."

Zander, 60, came to Motorola from Sun Microsystems in 2004. He greatly bolstered the company's fortunes with the introduction of the ultraslim Razr cell phone, which has sold more than 100 million units.

Soon afterward, however, Motorola was caught flat-footed by the introduction of the higher-bandwidth smartphone and by cutthroat pricing. Sales tumbled, and Icahn, who has a 3 percent stake in the company, called for his ouster.

After rounds of cost cutting, Motorola last month reported a better-than-expected profit for the third quarter. But it was apparently not enough.

Brown was chief executive of Micromuse, a network-management software company, before joining Motorola in 2003. Brown headed four different businesses at Motorola and led the company's $3.9 billion acquisition of Symbol Technologies.

"I welcome this opportunity to lead Motorola successfully into the future," Brown said. "We have a lot to do, and I am intensely focused on building shareholder value. I look forward to working closely with Ed to ensure a smooth transition."