Twelve top sprinters, headed by the champion filly, Safely Kept, were pre-entered yesterday for the first running of the Frank J. De Francis Memorial Dash at Pimlico Aug. 18.

The new race, which honors the late president of Pimlico and Laurel, will offer a $350,000 purse, making it the second-richest sprint in the United States. Because lucrative opportunities for six-furlong specialists are so rare, horses from all sections of the country will be shipping to Maryland for the event.

Safely Kept, the 4-year-old who was bred in Maryland and launched her career here, is the unquestioned star of the field. She has won 13 of 14 starts over the last two years, with only a photo finish loss in the Breeders' Cup Sprint marring her record.

Housebuster, the brilliant 3-year-old who has defeated the likes of Easy Goer and Summer Squall this year, also was kept eligible for the De Francis, and if he were to run the race would be a true championship confrontation. However, trainer Jimmy Croll has indicated that he would prefer to keep the speedster running in his own age group for most of the year, and Pimlico officials acknowledged that Housebuster is a doubtful starter.

The other 10 horses whose owners paid the $3,000 pre-entry fee all are likely to challenge Safely Kept. The top contenders include:

Sunny Blossom, a California-based speedster who shipped East this spring and won an Aqueduct stakes by nearly six lengths in lightning-fast time.

Beau Genius, a top midwestern sprinter who proved his versatility by winning the 1 1/8-mile Arlington Challenge Cup last Saturday.

Fire Plug, an indefatigable gelding from Philadelphia Park who has won 23 of 42 career starts.

Others in the prospective lineup for the De Francis Memorial Dash include Sewickley, Glitterman, For Really, Kechi, Lord March, Northern Wolf and Brave Adventure.

The race will be telecast nationally by ABC as part of the program covering the Travers Stakes from Saratoga.