Victor S. Kamber, who graduated from the Nixon White House and the AFL-CIO's Building Trade Council, founded his labor-oriented public relations firm five years ago with three associates.

Now, business is booming. The Kamber Group has 55 employes and five job vacancies, and has grown by 40 percent since October. It's become one of the top PR firms in Washington, with seven separate divisions that extend its services into advertising, direct mail and politics as well as plain old PR. Its billings last year totaled about $2 million, and Kamber expects the company could grow to as many as 75 or 80 persons.

The Kamber Group's growth is typical of the explosion that currently is taking place in Washington PR circles.

* Gray & Co., founded four years ago, remains Washington's largest firm, with $12.8 million in billings during the first three quarters of last year and 95 employes, many of them with star-studded names. The company, which went public last year, expanded so fast that it outgrew the former Georgetown generating plant that Gray named The Power House and took over three floors in The Flour Mill, a building across the street.

* Burson-Marsteller, the largest public relations firm in the country, billed about $4 million last year through its Washington branch and is considered the second-largest in the city. The local office has doubled in size in the past 18 months -- "a function of a market that has exploded," said its head, John Jessor -- to 47 people. Jessor expects the office to double in size again this year as the new hires bring in more clients.

* Hill and Knowlton, which was knocked to second place in last year's rankings of the largest PR firms in the country, maintains an office with 56 professionals in Washington. Most of its corporate clients are "system fed," said Bob John Robison, or referred by branches scattered around the world.

* Ogilvy & Mathers, the fifth-largest international public relations firm, opened its Washington office four years ago determined to attract its own clients instead of depending on referrals from other offices. Its client base is about one-third labor and nonprofit organizations, one-third trade associations and one-third corporate, reflecting the labor background of its chief, Mike Dowling, who came from the American Federation of State, County and Muncipal Employes to open the PR office. It employs 25 people and expects to add four or five more over the next year. The Washington operation pulled in $2.3 million in fees last year.