In the third renewal of The Washington Post's handicapping contest, Mickey Bogino (Mc. Bo) will defend her coveted position in a 24-night battle of imaginary $1,000 bankrolls starting Thursday at Rosecroft.

Her opposition, selected by a panel of Post judges from mofre than 400 applications, will be:

CHOMPERS - The first paired entry to be selected, dr Ronald Buro (32) and Dr. Mark Breslerman (32A), are Washington dentists with a flare for handicapping. "We earned our way through dental school at the track," declared Breslerman.

"Horse racing, like dentistry, is a science," he continued. "And remember, if a gelding has an abscess, and the codeine you must fetch, the horse will be a terror when driving down the stretch."

BERNIE HARRIS - A writer-editor for the U.S. Customs service. He had been handicapping seriously for 16 years and promises to share all his wisdom with his readers. "All Customs is depending on me," he said.

STUART SESSIONS - Compared to his job with the Office of Management and Budget, he said, picking winners is "like taking candy from a baby." He appears to be an aggressive bettor.

And how will Ms. Bo fend off such talent? "With my usual expert knowledge and lots of luck," she said.

Each contestant has an imaginary $1,000 to bet, with these requirements: at least three bets a night, a minimum of $2 and a maximum of $50 bet per race and only win, place and show wagering.

The person (or entry) with the most money after 24 nights will be The Post's harness-racing handicapper to the 1978 season.

A special thanks to everyone who applied. Those passed over, please try next time.