Robert Keith Gray never leaves home without his limousine and driver.

Jeb Brown prefers to pilot his own Porsche.

Despite their different driving styles, the two communications executives are on the road to putting Washington on the map as an advertising, public relations and marketing city.

Jeb Brown's goal is to make Earle Palmer Brown, the advertising agency founded by his father, into the biggest shop this side of Madison Avenue.

Bob Gray's goal is to turn Gray & Co. into the biggest public communications agency in the world.

Both are well on their way as the result of a pair of mergers that have been negotiated and are scheduled to be completed in the next few weeks.

The Earle Palmer Brown Agency has been the biggest in Washington for some time, but until now that was very much a big fish/small pond phenomenon.

This has never been much of a town for advertising and marketing agencies. The ad business was mostly retail accounts and the biggest marketing operations were the direct marketing (mail and phone) shops that specialized in raising funds for politicians and causes.

But Brown says the agency's billings should hit $90 million this year. That's better than three times the $26 million billed in 1981 and a very healthy number for someone outside the media centers of New York, Chicago or Los Angeles.

The growth that enabled Brown and company to move into three floors of a building in Bethesda this summer has come from diversification and acquisition. The planned merger with a Philadelphia agency this fall should help expand the geographic base of the business, which has been a goal for some time.

Last year, Brown made a pass at a Baltimore agency. An engagement was announced, but no marriage resulted because the two turned out not to be as compatible as they'd first thought, says Brown. He's continuing to look north and south for another geographic growth opportunity.

Baltimore and Richmond are potentially better ad markets than Washington, with big packaged-goods accounts like McCormick spice, Reynolds tobacco and aluminum, A. H. Robins drugs and Noxema. That business mostly goes to New York, but it is a tempting target for an adman.

An even more tempting target for public relations people is the hi-tech business incubating around the Washington beltway. Bob Gray outfoxed his competitors for that business last week by making a deal to merge with a firm that has offices in Silicon Valley, the Boston computer belt and techno-Texas.

Going hi-tech was an unexpected move for Gray & Co. Their stock in trade has been peddling influence and political acumen rather than intergrated circuits and biotechnology.

But Gray has quietly added some business strategy specialists to his stable of pols and the trend toward technology is even easier to measure than President Reagan's lead in the polls.

Marketing strategies, financial relations and corporate development will be more important to Gray's new clients than blue smoke and mirrors, and that is the direction the firm is headed. Gray is not going to be the flack who passes out press releases on new computers, but rather the mentor who advises emerging techno-magnates on their best avenues for growth.

Gray's own growth curve is impressive. Revenue was up 48 percent last year to $11.5 million and profits climbed 220 percent to $1.1 million. The cash raised when the company went public last spring will easily finance a couple more mergers. If the hi-tech trick proves as successful as it looks, Gray could well become the biggest man in his business.

Another Washington businessman who took his act on the road and wowed the world was Irvin Feld, the owner of Ringling Bros. and Barnum & Bailey Circus, who died Thursday after suffering a cerebral hemorrhage at the circus's clown college in Florida.

The diminutive ringmaster of The Greatest Show on Earth was surely the Greatest Showman in Washington, the man who brought thrills, chills and excitement to children of all ages.

Ringling Bros. was a tattered tent show when Feld, his brother and other investors bought it in 1967. The big top literally meant big overhead. Recognizing that canvas to house a circus was as archaic as canvas to power a ship, Feld folded the tents and took the show indoors.

He sold the show to the Mattel toy company a few years later and then in 1982, Feld and his family bought it back, proclaiming with characteristic quotability: "The good Lord never meant for a circus to be owned by a corporation."

One struggling show became two tantalizing touring companies under Feld's leadership. The parading pachyderms multiplied like rabbits from a ringmaster's hat. From Europe and Latin America he recruited whole families of performers. Michu, the world's smallest man, teamed up with Gunther Gebel Williams, the bare-chested lion keeper, and for those who found lions too tame, Feld produced Charlie Bauman and his trained tigers.

Catering to children raised on the televised dazzle of Disney, Feld picked up the pace of the show and packed the rings with nonstop entertainment. For the Star Wars generation, he brought special effects, replacing the bigtop ballerinas in the highwire acts with flame-belching motorcyclists high above the center ring.

"I would like to be remembered for having made a contribution to the continuance of the circus," Feld once said.

He certainly earned that legacy. Without Irvin Feld, this generation of American children probably would never see a three-ring circus. The Big Top could have gone the way of Chautauqua, had he not come along.

Irvin Feld will always be remembered as a center-ring act.