CHICAGO — Shares of McDonald's Corp., the world's largest restaurant operator, have rebounded in the past few months to levels not seen in more than six years.

The climb comes on the heels of a 50 percent boost in the company's dividend and pressure from a hedge fund manager threatening a proxy fight. The company's stock has risen more than 25 percent from the July 14 close of $33.04 to Friday's closing price of $42.11 on news that September sales were stronger than expected and third-quarter profits would exceed expectations.

The upside surprise from the world's largest fast-food chain prompted several analysts to upgrade McDonald's stock. The last time the company's stock was at these levels was in the summer of 1999.

For Chicago-based Morningstar Inc., a financial-services company, the sudden increase justifies the firm's belief that the stock had room to rise.

"We were very bullish on McDonald's at the end of May," said John Owens, Morningstar's restaurant analyst, noting Morningstar had boosted its rating of the stock to five stars.

"We felt the stock was undervalued," he said, noting that, like other restaurants, McDonald's was being unfairly punished because of high oil and gasoline prices.

But Janna Sampson, co-manager of the AmSouth Select Equity Fund and director of portfolio management at Oakbrook Investments, said it also didn't hurt that William Ackman, general partner of Pershing Square Capital Management LP, was "pounding on the table," threatening a proxy fight.

Ackman, who would not comment for this story, has said that despite the rise, shares of McDonald's are still undervalued by more than one-third. He has said the company's stock is worth $61 a share, and has repeatedly called for McDonald's to sell its interest in nearly 2,000 company-owned restaurants.

Ackman has been soliciting investors to help him buy as much as $2 billion in McDonald's shares to help wage the proxy fight.

The latest jump in the firm's stock occurred Thursday when McDonald's said it would easily beat Wall Street estimates for third-quarter earnings. New offerings, including premium coffee and a snack wrap, were driving more customers through its stores, it said.

Wall Street had predicted McDonald's would earn 63 cents per share, according to a survey of analysts by First Call, a financial-service company. McDonald's, however, said its earnings were expected to be 68 cents, or nearly 8 percent higher, and 17 percent higher than a year ago.

The company also disclosed that European sales, which had been struggling for the past two years, rose 7.6 percent for the quarter, while U.S. sales were up 4.1 percent for the quarter.

Also helping boost the company's stock was the disclosure that McDonald's had completed the disposal of its stake in Chipotle Mexican Grill Inc.

McDonald's said its shareholders traded 18.6 million McDonald's shares for the 16.5 million shares, or 82.2 percent stake, it held in Chipotle. The exchange reduced McDonald's shares outstanding by about 1.5 percent.

The firm's surprise sales results and earnings forecast, followed by its stock rally, helped push the Dow Jones industrial average into record territory.

Jim Skinner, McDonald's chief executive, said the quarter's sales figures demonstrate that the changes the company has pushed for three years are "powering sustainable momentum in our business with every area of the world once again posting strong comparable sales growth."

"We are increasing relevance, enhancing menu variety and improving customer convenience," Skinner said.

Sampson said the turnaround in McDonald's shares is what the investment firm has been expecting.

"As we go through the recovery in the U.S. we expected Europe to follow. Now we are seeing the plan to win work in Europe," she said of the plan adopted three years ago by McDonald's to boost its operations.