ManTech Sells Ownership in U.K. Joint Venture.

FAIRFAX, Va. -- ManTech International Corporation (Nasdaq:MANT), a leading provider of innovative technologies and solutions focused on mission-critical national security programs for the Intelligence Community and the Departments of Defense, State, Homeland Security, Justice and other U.S. federal government customers, announced today that it has concluded the sale of its 40 percent interest in the Vosper-ManTech joint venture in the United Kingdom. The joint venture was formed in 1996 between Vosper Thornycroft, a major UK defense contractor, and ManTech, to perform significant services for the GCHQ, a UK Intelligence agency. ManTech received cash consideration totaling GBP 2.5 million or approximately $4.4 million U.S. (based on the thirty-day average exchange rate), which includes the sale of its ownership interest and accrued dividends. The proceeds will provide approximately $1.6 million in pre-tax income in the fourth quarter.

About ManTech International Corporation:

Headquartered in Fairfax, Virginia, ManTech International Corporation is a leading provider of innovative technologies and solutions for mission-critical national security programs for the Intelligence Community and the Departments of Defense, State, Homeland Security, Justice and other U.S. federal government customers. ManTech's expertise includes systems engineering, systems integration, technology and software development, enterprise security architecture, information assurance, intelligence operations support, network and critical infrastructure protection, information technology, communications integration and engineering support. The company supports the advanced telecommunications systems that are used in Operation Iraqi Freedom and in other parts of the world; provides the physical and cyber security to protect U.S. embassies all over the world; has developed a secure, collaborative communications system for the U.S. Department of Homeland Security; and is helping the Department of Justice's U.S. Marshals Service deploy a common, office automation system. With projected 2005 revenues of approximately $1 billion and over 6,000 highly qualified employees, the company operates in the United States and 38 countries worldwide. In 2004, ManTech was selected by Business Week magazine as one of the Top 100 Hot Growth Companies and ranked by VARBusiness magazine as one of its Top 50 Fastest-Growing Solution Providers. Additional information on ManTech can be found at www.mantech.com.

Forward-Looking Information:

Statements and assumptions made in this press release, which do not address historical facts, constitute "forward-looking" statements that ManTech believes to be within the definition in the Private Securities Litigation Reform Act of 1995 and involve risks and uncertainties, many of which are outside of our control. Such forward-looking statements are subject to factors that could cause actual results to differ materially from those anticipated results. These factors include but are not limited to: the failure of the government to allot funds to ManTech to complete performance of the contact or exercise contract options; the risk of contract performance; government contract procurement (such as bid protest) and termination risks; competitive factors such as pricing pressures and/or competition to hire and retain employees; and material changes in laws or regulations applicable to the company's businesses. These and other risk factors are more fully discussed in the section entitled "Risks Related to the Company's Business" in ManTech's Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 16, 2005, and, from time to time, in ManTech's other filings with the Securities and Exchange Commission, including among others, its reports on Form 10-Q and Form 8-K. The forward-looking statements included in this news release are only made as of the date of this news release and ManTech undertakes no obligation to publicly update any of the forward-looking statements made herein, whether as a result of new information, subsequent events or circumstances, changes in expectations or otherwise.