* Ztango, a Reston company that sells wireless services, said it merged with MobileSpring, a New York-based text-messaging firm. Financial terms of the deal were not released. The merged company will be called Ztango. MobileSpring founder Mark Caron will become Ztango's chief executive. Vern Poyner, Ztango's former chief executive, will become its president and chief operating officer. No layoffs are expected as a result of the deal, and the combined company will have about 40 employees. Ztango plans to be based in Reston but maintain an office in New York.

* Paratek Microwave, a Columbia-based maker of wireless equipment, named James V. DiLorenzo president and chief executive. DiLorenzo, who replaced interim chief executive Tom Scholl, previously worked as the president of Signal Technology, a company Paratek acquired in November. Before that, DiLorenzo was a general manager of Raytheon Microelectronics.

* Surety, a Herndon-based security software company, named Tom Klaff chief executive. Klaff previously worked as the president and chief executive of Reliacast. Separately, Surety said it received $2 million from one of its original investors, Zenerji, and plans to use the funding for sales and marketing.

* SI International of Reston said it is maintaining its earnings and revenue guidance for its fiscal first quarter and full year. "We are aware that investors are concerned about the federal government IT market sector as a result of the delay in approving the . . . federal civilian spending bills and possible war with Iraq," chief executive Ray J. Oleson said in a news release. "We were sensitive to these uncertainties when we made our revenue projections" for this fiscal year, he said. The provider of information technology services backed its outlook from last month for a first-quarter profit of $1 million to $1.3 million (12 to 15 cents per share) on revenue of $37 million to $39 million. For the year, SI International expects earnings of $6.1 million to $7 million (72 cents to 78 cents) on revenue of $164 million to $170 million. Last year the company reported a loss of 3 cents per share, despite net income of $529,000, because of a debt repayment. It reported annual revenue of $149.4 million.

Compiled from reports by Washington Post staff writers, washingtonpost.com and Dow Jones News Service