A pair of investment firms have agreed to acquire Alltel Corp., the fifth-biggest U.S. wireless company and owner of the nation's largest geographic network, in a deal worth $24.8 billion.

The telecommunications company announced Sunday that it had signed an agreement to be acquired by TPG Capital, formerly Texas Pacific Group, and GS Capital Partners, a subsidiary of Goldman Sachs. The investors also agreed to take on Alltel's $2.7 billion in debt.

"This transaction delivers substantial and certain value to our shareholders while providing the company with long-term partners who share our commitment to our customers, employees and the communities we serve," Scott Ford, Alltel's chief executive, said in a news release.

"This transaction also ensures our customers can continue to rely on Alltel to deliver high-quality service and leading edge products and services."

The deal, if approved by shareholders and regulators, is expected to close during the fourth quarter of this year or the first three months of 2008, Alltel said.

Alltel has about 12 million cell-phone customers, mainly in the South, West and Midwest. That ranks it fifth in number of customers, after Cingular, Verizon, Sprint and T-Mobile, but the company's service "footprint" is larger than any of those rivals, Ford said.

The agreement calls for the two investment firms to acquire all of the outstanding common stock of Alltel for $71.50 per share in cash. According to Alltel, that represents a 23 percent premium over Alltel's share price before word of a possible buyout first appeared in the media on Dec. 29.

Trading in Alltel's stock closed Friday at $65.21, down 14 cents from the day before. The $71.50 per share buyout price would represent a premium of only about 10 percent over Friday's share price.

Ford said in a telephone interview that the buyout price is "a 10 percent premium over a price that clearly anticipated this outcome" after scores of articles had been written about Alltel's prospects in the first months of this year.

The announcement was the second in a week of a buyout of a corporation based at Little Rock to be taken private by the new owners. On Wednesday, data-management firm Acxiom Corp. announced it was to be acquired in a buyout worth about $2.25 billion.

Ford said in the phone interview that the Alltel deal resulted from "a very thoughtful, very careful, very thorough review" over several months by the Alltel board of the best options for assuring the company would be able to continue serving well both its customers and its shareholders.

"The shareholders got what we feel is the best deal we could have gotten for them," he said.

Ford said the company's headquarters would remain in Little Rock, and no changes were planned in staffing. The company has about 15,000 employees, he said.

"We're a pretty lean organization as it is," Ford said.

Alltel has streamlined in recent years, first selling its information system division in 2003 and, last year, spinning off its wireline business. That left Alltel as a pure wireless company. In its first-quarter earnings released early this month, Alltel reported that income from its continuing operations increased 34 percent to $225.4 million, or 63 cents per share, from $168.6 million, or 43 cents per share, a year ago. Revenue grew 13 percent to $2.08 billion from $1.84 billion.

Alltel has seen its growth driven by its "My Circle" calling plan, which allows free calling to any 10 numbers.

TPG Capital is the global buyout group of TPG, a private investment firm founded in 1992, with more than $30 billion in assets under management, according to the Alltel release.

GSCP is the "private equity vehicle" through which The Goldman Sachs Group Inc. conducts privately negotiated acquisitions.