IT was an idyllic Vermont view from halfway up Burke Mountain. A patchwork of forest and pasture rolled westward to a distant mountain ridge. Puffy white clouds hung in a blue sky. But I was focused on a brown ribbon that plunged down the slope like a dirt bobsled track, nervously clenching the handlebars of a hulking bicycle that resembled a motocross motorcycle.

“Try to relax,” my instructor, Lilias Ide, was saying to me and six other middle-aged mountain bikers.

I had come to Vermont’s northeast corner on the advice of a friend who had heard me complaining about the roots and rocks that make many New England mountain bike trails so jarring. In this area, known as the Northeast Kingdom, instead of teeth-rattling boulders, glaciers had deposited a massive ridge of sand known as Darling Hill.

Local die-hard mountain bikers knew a good thing when they saw it. Over the last 20 years — first as an impromptu group of bike fanatics, later as the nonprofit Kingdom Trail Association — they adopted defunct cross-country ski trails and carved new ones. The result is the Kingdom Trails, a network of more than 100 miles. Bike Magazine declared it the best trail system in North America for 2008.

Cashing in on the enthusiasm, two years ago the local Burke Mountain Resort opened a chairlift in the summer to ferry mountain bikers to the top of a ski run, charging them $30 for a day pass. Last year the trail association started offering downhill classes, dubbed “Gravity School,” aimed squarely at people like me.

Though cross-country mountain biking is my preferred niche, I had watched downhill riding — in which cyclists plunge down precipitous mountains, cliffs or, in this case, ski runs — from afar, half awed and half mystified at the sport’s allure. Now, with an instructor and rental gear, including bikes with huge shock absorbers, extra-wide tires and hefty disc brakes, this was my chance to see what it was all about.

AS we prepared to descend, Ms. Ide offered some advice in a casual, matter-of-fact way that mirrored both her expertise and her outfit. While we all wore white plastic armor that had us resembling riot police, she was on a pink bike bearing the brand name Sinister, wearing baggy shorts and kneepads. Huge silver hoop earrings poked out from under her helmet.

Look down the trail to see what’s coming, not directly in front of your wheel, she told us. Look where you want to go, because that’s where you will steer. Don’t sit down. Standing on the pedals keeps you nimble.

We opened with an appetizer of sorts. With Ms. Ide in the lead, we rolled single file over little humps and through sweeping turns for several hundred yards. No problem. Ms. Ide stopped and previewed the section ahead. It was a set of downhill snaking curves with high, banked sides, one right after the other. I set off with a tightening in my gut. Nearly shooting straight into dirt walls as I twisted and turned around the course, I found myself locking up the brakes and staring at my front wheel, willing it to not fly off the uphill lip of the trail. Somehow, I arrived at the bottom unscathed and jittery with adrenaline.

Forty-five minutes and several runs later, we steered toward Knightslayer, the area’s premier downhill run. The map showed two black diamonds on it: experts only. It was a slender trail snaking through a forest of maple trees and studded with jumps built from mounds of dirt. The most ubiquitous were “tabletops” — steep six-foot-tall ramps, topped with a plateau and ending in another plunging slope. The best riders zip up the ramp, fly over the top and land on the far side. The less brave jump onto the plateau and roll down. At the first tabletop, I barely worked up enough nerve and speed to creep up and onto the top. At that moment my biggest fear was losing so much speed that I would stop on the ramp and fall over backward — an embarrassment I narrowly avoided.