The Maxima Corp., a computer services and products firm in Rockville, has been named company of the year by Black Enterprise magazine, which also lists seven Washington-area companies among this year's most successful black-owned businesses.

In announcing its 14th annual list of the top 100 black-owned businesses, Black Enterprise also cited 10 companies for having the highest growth rates during 1985. Mandex Inc., a Washington telecommunications, engineering and computer services company, ranked second among BE's fastest growing companies, based on a 99 percent increase in sales to $16.2 million in 1985. The surge in Mandex's sales placed it on BE's Top 100 list for the first time.

The clearest evidence of growth potential among black-owned companies, said Black Enterprise's editors, can be found in the BE 100 company of the year. The Maxima Corp., they noted, jumped from No. 100 two years ago to its current position as No. 27. Started with only one employe in 1978 by President and Chief Executive Officer Joshua Smith, Maxima has had an annual growth rate of 35 percent, according to BE.

Other Washington-area companies on this year's BE Top 100 list are Systems and Applied Sciences Corp. (SASC), a computer and electronic-data-systems firm in Vienna; Joe McLaughlin Oldsmobile Inc. of Capitol Heights; Seidel Chevrolet Inc. of Landover; International Business Services Inc., a Washington computer services company; and Unified Services Inc. of D.C., a general construction firm and provider of janitorial services and supplies.

Seidel Chevrolet and Unified Services also made the BE Top 100 for the first time.

Combined sales of the seven Washington-area companies were $162 million in 1985, according to Black Enterprise. SASC, which reported sales of $58 million in 1985 is, by far, the largest Washington-area company on this year's BE Top 100 list, featured in the June issue of the magazine. SASC moved up a notch, from 10th on last year's list.

International Business Services Inc. (IBS), which ranked 73rd on last year's list, dropped to 97th, even though sales were flat, according to figures provided by BE. Although the magazine reports sales of $14 million for IBS, Marion Greene, the company's founder and president, recently put revenue at $28 million. In the meantime, IBS has been sold to Comarco Inc., a California high-technology company that operates it as a subsidiary.

In Black Enterprise's separate rankings of financial institutions, two D.C. banks, Industrial Bank of Washington and United National Bank, are ranked fifth and sixth, respectively, among the 44 U.S. banks controlled by blacks. Universal Bank of the Lanham-Seabrook area of Prince George's County is ranked No. 43. Washington's Independence Federal Savings Bank is the second-largest black-owned thrift institution in the United States, according to BE. Financial institutions controlled by blacks in the D.C. area had assets of $325 million in 1985.

Sales for all BE 100 companies rose 14.8 percent, from $2.6 billion in 1984 to $2.94 billion in 1985. Johnson Publishing Co. Inc., the giant Chicago media and cosmetics company whose publications include Ebony and Jet magazines, grossed $154.9 million in sales last year, making it the No. 1 ranked company on the BE Top 100 list for the third consecutive year. Motown Industries of Los Angeles is second for the third consecutive year. The nationally known entertainment company reported $139 million in revenue for 1985.