(MONEY Magazine) – It is dusk, and you are standing waist-deep in the cold waters of the Beaverkill River in New York's Catskill Mountains, fabled among fishermen for a century for its brown trout. You sweep the tip of your Orvis graphite rod back, then artfully cast your Hendrickson fly -- a tiny hook wrapped in bits of fur and feathers -- so that it lands softly on the glassy surface. Suddenly the water erupts and the fly disappears. You lift the line firmly to set the hook, then slowly reel in a fiercely struggling 18-inch Salmo trutta. Such is the fantasy that is attracting a growing number of people, many of them young professionals seeking an antidote to the pressures of urban life, + to the ancient and arcane sport of fly-fishing. John D. Randolph, editor of Fly Fisherman magazine, estimates that about 5 million men and women fish with flies today and that their ranks are increasing by 10% to 15% a year. The great majority casually cast for rainbow, brook or brown trout in lakes and streams near their homes. But about one in 10 becomes what Randolph calls a ''hard-core fanatic'' who builds his or her own rods, ties his or her own flies and seeks more exotic species, such as steelhead trout and Atlantic salmon, in remote and scenic waters from Alaska to Iceland. Once caught, the quarry is usually released. The challenge for enthusiasts is in stalking and fooling a fish into taking the fly; after it is hooked, aficionados generally regard the rest as anticlimactic. While you can learn the rudiments of fly-fishing on your own, few people can master the sport without expert instruction. A successful angler must not only know how to cast a nearly weightless fly 50 or 60 feet but also understand what type (there are thousands) is most likely to appeal to a fish, given the weather and the kind of water he or she is fishing. You also need to manipulate the fly so that it mimics the movements of the insects or minnows fish are feeding on at that particular moment. The best fly-fishing courses, including those of such nationally known schools as L.L. Bean in Freeport, Maine and Orvis in Manchester, Vt., last two to three days, usually over a weekend, and cost $300 to $550, including meals and lodging. But at least one well-respected company, the Mel Krieger School of Fly Fishing and Casting in San Francisco, supplements two days of intensive instruction in the classroom and outdoors with four days of fishing with an instructor on streams in Idaho and Montana for $1,400. Most schools assign no more than seven students to each teacher and include classroom and field instruction in all aspects of the sport, from casting and wading techniques to knot tying. A few schools require you to bring your own equipment (see the box). Students normally practice in streams, though some schools also provide instruction on well-stocked trout ponds. If you are not ready to commit much time or money to learning the sport, you may want to consider the half-day or full-day fishing clinics that are offered by a few schools and many fishing supply stores, including five Orvis branches across the country. These mini-courses, which usually run from $50 to $100, mostly emphasize casting techniques. Or, if you would prefer more personal attention, some schools, resorts and stores will provide one-on-one instruction for $12 to $35 an hour. Before signing up, make sure your instructor will be someone who is experienced in teaching, not just fishing. The following is a region-by-region list of organizations that offer fly- fishing instruction. Unless otherwise stated, these prices do not include meals and lodging. It's probably a good idea to make reservations for multiday courses at least a month in advance, especially during the peak spring and summer in the Northeast.

NORTHEAST

L.L. Bean Fly Fishing Schools, Freeport, Maine 04033; 800-341-4341 L.L. Bean, famous for its mail-order catalogues, offers introductory and intermediate fly-fishing schools directed by Dave Whitlock, one of the best- known masters of the sport. The three-day basic course conducted at streams near the store, Friday through Sunday, April through June, costs $315. (The price includes a rod, reel and line.) The four-day intermediate course ($495) emphasizes in-stream instruction. Orvis Fly Fishing School, Manchester, Vt. 05254; 802-362-3900 Orvis, one of the grand old names in American fly-fishing, offers three-day programs at its Vermont headquarters for $430 ($415 for weekday schools), including room and partial board at the nearby Equinox Inn. Joan and Lee Wulff Fishing School, P.O. Box 16 MM, Lew Beach, N.Y. 12753; 914-439-4060 Joan Wulff is a world-champion fly caster; her husband Lee is one of fly- fishing's Olympian figures. Their school on the Beaverkill River runs Friday to Sunday, April through June, for $320. Jones Outfitters, 37 Main St., Lake Placid, N.Y. 12946; 518-523-3468 This fishing supply shop near the famed Ausable River in New York's Adirondack Mountains offers a 1 1/2-day school on weekends, May and June. The $195 fee includes food and lodging. The Sporting Gentleman, 306 E. Baltimore Pike, Media, Pa. 19063; 215-565-6140 This shop runs two weekend schools each spring -- one in Media, a Philadelphia suburb ($125), the other in the Pocono Mountains ($295, including food and lodging). One school each year is for women only.

Beckies Fly Fishing Specialists, 1336 Orange St., Berwick, Pa. 18603; 717-752-2011 Barry and Cathy Beck provide one-on-one fishing instruction for beginners or experienced anglers on Fishing Creek in northeastern Pennsylvania. The one-day program costs $125. Slate Run Tackle Shop, Slate Run, Pa. 17769; 717-753-8551 This north-central Pennsylvania store offers a three-day weekend school only in May and June for $260 (includes lodging and some meals), as well as one-on- one instruction for $90 a day.

SOUTHEAST

The Happy Hiker, Chestnut St., Highlands, N.C. 28741; 704-526-5298 A 2 1/2-day school in the Blue Ridge Mountains, April through October, for $325 weekdays, $350 weekends. Instruction covers tactics for bass and trout. Fish Hawk Fly-Fishing School, 283 Buckhead, Atlanta, Ga. 30305; 404-237-3473 This 2 1/2-day school, held year round, focuses on fly-fishing for brown and rainbow trout. Cost: $295.

MIDWEST

Bright Waters Fly-Fishing Schools, 3803 Grand Ave. South, Minneapolis, Minn. 55409; 612-825-5524 Weekend half-day casting clinics ($35 to $55) and one-day streamside clinics ($55) are offered April through August. Gates AuSable Lodge, Rte. 2, Box 3336, Grayling, Mich. 49738; 517-348-8462 Guide Rusty Gates gives one-on-one casting lessons and in-stream instruction ($15 an hour, $20 for two people, minimum half-day). Thornapple Orvis Shop, Thornapple Village, Ada, Mich. 49301; 616-676-0177 Weekend classes are held May and June and divided into a Saturday casting session and Sunday instruction on the nearby Rogue River ($90 a day; students can sign up for the entire course or for either one-day session). Outdoors Inc., 9755 Clayton Rd., St. Louis, Mo. 63124; 314-997-5866 Three-day schools, April through October, are conducted at Rainbow Trout Ranch in the Ozarks village of Rockbridge, Mo. Cost: $300. P.J.'s Resort Lodge Schools, P.O. Box 61, Norfork, Ark. 72658; 501-499-7500 This lodge offers beginning and advanced three-day courses, February through November ($295, lodging and meals included).

SOUTHWEST

Orvis Houston Schools, 5848 Westheimer Rd., Houston, Texas 77057; 713-783-2111 Orvis' Houston outlet provides one-on-one casting instruction for $50 per 90 minutes and schools tailored to the needs of specific groups, including beginners. Call the store for dates and prices.

ROCKIES

The Flyfisher, 252 Clayton St., Denver, Colo. 80206; 303-322-5014 | Three-day weekend schools are offered in June, July and August at Elktrout Lodge on the Colorado River for $475, including meals and lodging. The Flyfisher also provides a two-evening casting course April to August in Denver for $45. Montana Troutfitters, 1716 W. Main St., Bozeman, Mont. 59715; 406-587-4707 This four-day school on the Gallatin, Madison and Yellowstone Rivers in the Rocky Mountains near Yellowstone National Park is held July and August and concludes with a day of guided fishing. The $698 fee includes food and lodging.

WEST COAST

Mel Krieger School of Fly Fishing and Casting, 790 27th Ave., San Francisco, Calif. 94121; 415-752-0192 Champion caster Mel Krieger schedules weekend courses April through September on rivers in Arizona, California, Oregon, Pennsylvania, Texas and Washington for $275 to $350, depending on location. He also conducts a program in Idaho and Montana featuring two days of instruction plus three or four days of guided fishing ($1,300 to $1,500, depending partly on location and season, meals and lodging included). Fall River Flyfishing Schools, The Fly Shop, 4140 Churn Creek Rd., Redding, Calif. 96002; 800-535-3474, outside California, 800-533-3474

These three-day schools on northern California's Fall River and Hat Creek are offered both weekends and weekdays in May, June, July and October for $450, meals and lodging included. Kaufmann's Fly Fishing Schools, P.O. Box 23032, Portland, Ore. 97223; 503-639-6400 Wet-fly expert Randall Kaufmann teaches this three-day school on Oregon's Deschutes River every week, May through October. The price of $295 includes food and lodging. Orvis West Coast Fly-Fishing Schools, 166 Maiden Lane, San Francisco, Calif. 94108; 415-392-1603 This branch offers schools for beginning and experienced anglers. Its basic three-day weekend course runs March through September at Tahoe, Carmel Valley and Sonoma County for $395, including some meals. A five-day program for students with some experience is held at Take It Easy Ranch in southern Oregon for $625, including room and board. Orvis also gives Sunday casting clinics in the Bay Area for $50 and a six-day school in October on fishing for steelhead, the Pacific sea-run rainbow ($995).

BOX: THE COSTS OF GETTING HOOKED Before you wade into fly-fishing, you will need to spend at least $135 on the following equipment:

-- Rod: $40 to $100 -- Reel: $15 to $500 -- Line: $10 to $35 -- 24 flies: $30 to $45 -- Hip boots: $35 to $95, or -- Chest waders: $100 to $175 -- Fly waterproofing: $1 to $3 -- Hook sharpener: $4 to $7