They rent horses, don't they?

Well, that depends.

There is nothing quite like the hypnotic, rhythmic pace, the smell of the horse's sweat and the itch and twitch of the horse's mane, as you ride, lord among branches.

"Most people want to ride out into the sunset," says Margaret Johnson, owner of the Great Falls Horse Center in Virginia. "They don't know anything about riding horses. They ruin your horses." At the center, they don't rent to people outside the equestrian school. "We could make a million if we did, we get so many calls. But we'd spend it all out in insurance," says Johnson.

In Upper Marlboro, the Merrymount Horse Center teaches riding and boards and breeds horses, but someone just off the street or the lone prairie can't rent a horse for a John Wayne Stetson.

Merrymount tried guided trail rides, where people rent horses and ride in groups, and found, says owner Bill Gladman, "The bad people hold up the good people and vice-versa." Trail rides, he says, are "almost going extinct."

"Trail ride horses are kind of the bottom of the barrel. It's an amusement-park business more or less," says Gladman.

Dealing with the neophyte presents other problems: "To put a person on a horse who's never been there is somewhat dangerous," he says. "Anything in the world can scare a horse -- a bird or a leaf. That's what worries us: if you get a guy or a girl on a horse and the horse takes off . . ."

But there are some places hereabouts that do rent horses, some without guides. In case it's been a long time since you learned to ride at summer camp, appropriate attire, without a major investment, is jeans, a helmet and riding boots if you have them. If you don't have boots, wear shoes with a slight heel -- not running shoes.

At a few of the stables, Western saddle is available. More ornate than the slip of an English saddle, Western is the saddle with a horn on the front where you loop your lasso or hold on for dear life.

ROCK CREEK PARK HORSE CENTER gives guided trail rides six days a week. No experience necessary. The hour-long ride takes in parts of 20 miles of bridle paths through the Park, from East-West Highway south to the Zoo. The rides are geared for beginners, who will have brief instruction, as well as for the trot- and-canter crowd. The center also makes provisions for the handicapped. Horses are English saddle.

Tuesday through Friday, trail rides leave at 1:30, 3, 4:15 and 5:30, and Saturday and Sunday at noon, 1:30, 3, 4:15 and 5:30. Cost is $7.50. Military and Glover Roads NW. Phone: 362-0117.

At BRANDYWINE STABLES, you can play cowboy and cowgirl, in Western or English saddle. Real cows graze in the fields, as well as zebras, camels, llamas, buffalos and ostriches, but they're harder to round up. On 450 acres of trails, fields, creeks and woods, you're on your own -- "unless you're young and beautiful, then I have to go," says manager Bill Grove. Open from 8 to 7 daily, and rental is $10 an hour. On Route 5 (Branch Avenue) 12 miles from Beltway exit 7A. Phone: 372-8914.

For people weighing under 90 pounds, there are pony rides on Sunday afternoons at MEADOWBROOK STABLES. Almost as tame are the guided trail rides, where horses go little faster than a walk. There's a temporary halt to rentals at Meadowbrook this month because of horse shows there; the stables plan to resume rides on May 23. Rides are Sunday afternoons starting at 1, 2 and 3 on trails through Rock Creek Park. Pony rides, $3.50, trail, $6.50, English saddle. 8200 Meadowbrook Lane, Chevy Chase. Phone: 588-6935.

WOODLAND HORSE FARM rents to qualified riders. What this means is they administer a test to affirm that you can walk, trot and canter a horse reasonably well. It is $5, and qualifiers get an identification card. Rentals are by appointment and cost $9 an hour. There are no guided rides. English riding. Hours: weekdays noon to 6:30, Saturdays and Sundays 9:30 to 1:30, closed Mondays. 16301 New Hampshire Avenue, Silver Spring. Phone: 421-9156.

Trails lead from WHEATON PARK STABLES and on through the park, but there's also an outdoor ring, and an indoor ring where you and your horse can seek shelter from wind and rain. Rentals are $6.50 an hour, by reservation. The folks at the stables recommend that beginners tag along with the escorted trail rides on Sundays at 2, 3 and 4. Otherwise, rentals are available on Tuesdays and Thursdays from 9:30 to noon, Wednesdays and Fridays from noon to 3 and Sundays from 8 to 3. English. At 1101 Glenallan Avenue, Wheaton. Phone: 622-2424.

For romantics, the POTOMAC EQUITATION FARM in Centreville, Virginia, guides evening rides on the trail after 8. These are especially popular in the summer when it's hot in the saddle. (English and Western available.) Otherwise, from 8 to 7 daily, horses are available for rent at $10 an hour. A guide can be rented for an additional $8 an hour. There are 160 acres of open trails, at 5320 Pleasant Valley Avenue, Centreville. Phone: 631-9720.