Shares of Omnipoint Corp. jumped 38 percent yesterday, a day after the Bethesda wireless phone company announced a $5 billion merger with VoiceStream Wireless Corp. that would create a new national cellular network.

An agreement would end a run of speculation about the fate of Omnipoint, an industry pioneer that analysts have viewed as a prime acquisition target for months.

Together, the companies hope to offer service that would compete with those of powerhouses such as AT&T Corp., Sprint Corp. and Nextel Communications Inc.

Under the terms of the deal, VoiceStream would pay 0.825 shares and $8 in cash for each share of Omnipoint. At today's prices, that comes to $31.51 per share, a 9.6 percent premium over yesterday's closing price.

Omnipoint shares jumped $7.93 3/4 to close at $28.75. VoiceStream dropped $1, to $28.50.

Both VoiceStream and Omnipoint use a technology called the global system for mobile communications, or GSM, a standard that is popular in Europe but less so in the United States.

VoiceStream has been hindered by its inability to offer service beyond a cluster of cities in the West. With a merger, the company would add service in major Northeast markets such as Boston and New York. The merger would also allow VoiceStream to reduce costs by combining administrative chores such as customer service and billing.

The Washington area's Sprint Spectrum service, which Sprint is discontinuing in favor of Sprint PCS service, uses GSM technology. Omnipoint founder and chief executive Douglas Smith said the combined company would want to serve Washington but declined comment on whether it might buy the Sprint Spectrum system.

Together, VoiceStream and Omnipoint have about 1 million subscribers and cover an area that is home to 175 million people. They would become the ninth-largest wireless company in the United States, analysts say.

"We've been anticipating a GSM roll-up for some time," said Mark Lowenstein, a global wireless analyst at the Yankee Group in Boston. The size of the VoiceStream-Omnipoint combination would allow it to negotiate more favorable "roaming" rates for its customers using other GSM systems, Lowenstein said.

Omnipoint, which was incorporated in 1987, employs about 2,000 people around the United States. Although it has its headquarters in Bethesda, the company's work force in the Washington area is only about 50 people, Smith said.

Smith said Omnipoint will continue to operate out of Bethesda, although the fate of its brand name has not yet been determined. Smith said he expects the deal to close in the fall, pending regulatory and shareholder approval.