For 15 hours and 88 miles, 10-year-old Danielle Kanavy had battled tough mountain terain and determined adult compeitors in a race that horse-conscious Virginians consider the ultimate test of stamina, conditioning and sheer willpower for steed and rider alike.

Leaving dumbfounded and admiring grown-up contestants far behind her, the littlest horsewoman had pushed her big bay mare subbornly and incessantly onward, to winin minutes of the lead.

Now, matted the grit and sweat, Danielle stood weary and inconsolable in the last light of the setting sun 12 miles from the finish line. A judge's decision forced her to wait in second place until her horse could catch its breath.

Her mothber's arms laced tenderly around her neck, Danielle choked back a sob as her chances for victory ebbed irretrievably away. Allowing a single tear of disappointment to fall unmolested down her cheek, Danielle watched her 40-year-old rival ride confidently across the Shanandoah and into the homeward stretch.

"From the beginning," said Danielle's mother, her own eyes brimming with tears," she wanted to win."

The focus of her misery was the annual Old Cominion 100-Mile Endurance Race, a contest of gruesome proportions run in a giant loop around Massanutten Mountain about 70 miles west of Washington. The course led up treacherous trails," across rivers and down gravel roads. Only the strongest survive. A silver cup and no little esteem are the sole rewards.

For Danielle Kanavy of Chester Springs, Pa., the last 12 miles of the Old Dominion race were the longest. Though it was no consolation to her, a score of those seeking to ride the distance never made it that far. Others did not see the finish line until they had spent a full 24 agonizing hours in the saddle.

"It was the hardest thing I've ever done," said Linda Crandell, the Annapolis piano instructor who won last year and who led the pack going into the final leg Saturday night. "It's the worse thing anybody will even do."

There were 80 entrants, half competing in the full-length race and the remainder in a shorter, 50-mile course. They came from as far as Canada to submit to the pounding heat, gruelinmg bumidity, man-eating bugs and rock-strewn trails this race had to offer. More than 25,000 feet of climbing lay between 5 a.m. Saturday, when the riders spurred their mounts onto the trail, and 10 p.m., when the first of the 100-mile survivors returned.

Of the handful of such races in the country, Old Dominion organizers termed this one "absolutely the most severe." For many it was just too much.

"Awful," said one rider.

"The last time I ever ride here," said another.

"You learn things about yourself," explained Nancy Lewis, a real estate agent from Roanoke. "You learn that you can keep going -- forever."

Not everybody did.

At various checkpoints, attending veterinarians with stethoscopes and thermometers closely monitored the condition of lathering beasts. Occasionally, as heart beats soared passed allowable limits, as body systems stretched beyond endurance, riders grimaced and wept when told they could not go on.

"You do it one mile at a time," was the ay 66-year-old Kay Fullerton of Deep River, Conn., irrepressible winner of the Old Dominion's first cup eight years ago, had explained on Friday her method of finishing the race. By midday Saturday, however, Fullerton was struggling to fight back tears when her mount failed muster at the 50-mile mark, another casualty of the punishing course.

From before dawn and well into the morning of the next day, the caravan twisted its way through what tourists find some of the most beautiful country in the state. But the views from thickly forested mountains quickly lost their appeal when penetrated at sheer angles on horseback.

Through wilderness places with such names as Peach Orchard Gap and the fearsome Sherman's Gap, last hurdle on the trail, contestants led their horses over steep and narrow paths. In areas demanding human footwork of a fancy sort, where ledges fell off into an oblivion of tangled greenery in the valleys below, metal shoes clopped slowly and ominously in the forest stillness. The hardiest riders dismounted and led their horses up; others, grabbing onto tails from behind, appreciated the one-horsepower pull.

"That sure is some hill," groaned one sweating rider, savoring the end of a 1,000-foot climb.

Horses and riders alike reveled in the cool trout streams that twist through the pines. Demanding and sometimes heartbreaking, the ride suddenly turned picturesque when a saddle-weary traveler, finding a rushing creek at the bottom of the mountain, dipped his steel riding helmet into water to refresh his panting charge.

And for two riders competing in the 50-mile event, there was the exhilaration of a race to the finish, where a newcomer from California overtook the seasoned favorite in the last hundred feet.

But in the final moments, all eyes turned to the woman/child who wanted to win so badly. After eagerly watering down her overheated horse, Danielle Kanavy reported too early for the veterinarian's inspection. The horse, Remeqwa Kaffara, was judged not ready and Kanavy suffered a further 10-minute penalty and the loss of the adult partner required to ride with her, who declined to wait.

In a final irony, it was Kanavy's partner in the race -- Connie Thompson of Honeybrook, Pa., the woman who wouldnht wait -- who went on to win, overtaking the exhausted leader in the last few miles.

ythe winning margin: 10 minutes and 53 seconds. Kanavy, trotting across the finish line shortly after 10 p.m., finished third, two seconds behind the woman she had tried all day to catch.