Forensics, consulting, information technology services, engineering. The small businesses showing the fastest growth in the government sector also showcase a variety of services and niches that contractors can thrive in. The top company, Global Analytic Information Technology Services Inc. of Springfield, Va., provides information technology services and has found customers such as the Army and the Agriculture Department. GAITS' government revenue grew at a compound annual rate of 171 percent between 1998 and 2002. The annual Fast 50 list returns to Washington Technology this year after residing in other PostNewsweek Tech Media publications. But the list has been reinvented. In past years, Fast 50 companies were ranked based on the growth of their total revenue. The Washington Technology Fast 50 ranks IT companies based solely on the growth of their government revenue. Twenty-one of this year's Fast 50 companies are IT services firms, and three of the top 10 firms provide consulting services. One of these, No. 2 immixGroup Inc. of McLean, Va., offers consulting services to companies that want to do business with government agencies. The company, founded by Jeff Copeland and Steve Charles in 1997, went from $974,000 in 1998 to about $49.4 million in 2002, a growth rate of 166.8 percent. At No. 8, Acquisition Solutions Inc. of Oakton, Va., has built its business by providing consulting services to government agencies that want to improve their procurement processes. Founded in 1996 by Chip Mather and Eben Townes, the company grew at a rate of 116 percent between 1998 and 2002, going from $475,000 to $10.3 million. Acquisition Solutions executives also write a column that is published in every other issue of Washington Technology. Led by Jay Jayamohan, Comter Systems Inc. of Fairfax, Va., rounds out the top 10 with a 101.8 percent growth rate between 1998 and 2002. The company provides consulting services in areas such as enterprise resource planning, infrastructure and architecture and information security. Its revenue grew from $338,000 in 1998 to $5.6 million in 2002. Other companies in the top 10 provide services such as systems integration, engineering and professional services. Guidance Software Inc. of Pasadena, Calif., is the only company in which providing computer forensics services is its main line of business. The company, which had a growth rate of 135.9 percent between 1998 and 2002, sells products and services that help agencies and companies investigate cyberattacks. Guidance isn't the only company that addresses a narrow niche. For example, No. 40 Dynamic Animation Systems Inc. of Fairfax, Va., creates virtual reality applications -- in other words, high-tech video games -- for training. For the National Fire Academy, Dynamic Animation built a simulation laboratory and a national simulation and training network. Dynamic Animation has seen its revenue grow by a compound annual rate of 55.6 percent, rising from about $1 million to $6.2 million between 1998 and 2002. Other categories that had multiple entries include professional services with two companies, engineering with three, software development and engineering with five, and systems integration with six. *