Starting today, Charles Edwards, 31, who was born without a left leg, plans to join the enthusiastic ranks of downhill skiers.

Although skiing is a sport that appears to require exceptional agility, Edwards is one of thousands of disabled people, young and old, heading for the nation's downhill (and cross-country) ski areas in search of the same exhilaration as other winter-sports enthusiasts. Edwards, who is staff director and general counsel of the House Aging Committee, has signed up for a week of beginners' lessons designed specifically for the physically handicapped.

At a time when growing numbers of the disabled are participating in all areas of contemporary life, skiing for the handicapped has become one of the nation's "fastest growing sports," says amputee Dave Fowler, 33, a ski instructor at Jack Frost Mountain, White Haven, Pa. He is also director of The 52 Association's amputee ski clinics, one of several national winter sports programs for the handicapped. Fowler lost a leg in 1971 when he stepped on a land mine in Vietnam.

Among those who are heading for the slopes: single and mutiple amputees, who use "outrigger" attachments on their poles; the blind (a guide skis alongside giving directions); victims of muscular impairments such as cerebral palsy and multiple sclerosis; the mentally disabled, and the wheelchair-bound paralyzed (who experience the thrill of speed in a toboggan-like device called the "sit ski").

There's even a national racing program--slalom, giant slalom, downhill and cross-country--sponsored by the National Handicapped Sports & Recreation Association of Washington. This year's National Handicapped Ski Championships are March 21-26 in Squaw Valley, Calif. The site is Red Dog, one of the resort's most challenging racing slopes.

After his Vietnam injury, Fowler was admitted to an Army rehabilitation program, where he learned to ski. When he encountered other amputees trying to learn at Jack Frost in 1974, he offered to help them and became a full-time instructor.

"There's something about skiing the slopes with the best of them," he says, "that gives you the confidence to do just about anything else you want to do."

Skiing, Fowler insists, "is easy," even for those missing one or more limbs. On the slopes, his disabled students often progress as fast as other beginners and in a matter of hours take their first ride up the chairlift. As with any novice, he teaches them first how to control their speed.

By week's end, many have full run of the mountain and can go on to ski anywhere. Fowler and his staff of specially trained instructors also offer lessons by appointment at Jack Frost (717-443-8425) to individuals and groups up to four.

Ski clinics for the handicapped are conducted annually at a number of other ski resorts in the United States and Canada. Last Thursday and Friday, for example, West Virginia's Monongalia County held a winter Special Olympics at Canaan Valley Resort for 65 participants, age 9 to 40, with mental disabilities. Local high schoolers were trained as instructors. Similarly, 135 mostly youngsters joined for four days last week in the West Virginia Special Olympics Winter Games at Wisp ski resort in western Maryland.

Edwards, who is participating in the Jack Frost clinic with about 100 other handicapped skiers, many from the Washington area, admits to a little apprehension about his first day on skis. "It's a big step," he says, "but I've waited a long time."

Among the largest programs for physically handicapped skiers:

* The 52 Association, Inc.: a nonprofit organization "serving the needs of the severely disabled" by building confidence through sports. This season's events include four clinics for amputees and one for the blind. A four-day clinic for amputees is under way this week at Jack Frost and the final one set for April 4-7 at Alpine Meadows Ski Area, Tahoe City, Calif., concluding April 8 with a championship race. Funded in part by The Southland Corp. (7-Eleven Stores), the annual program pays for lodging, food, instruction and loaned equipment. For information: 441 Lexington Ave., New York 10017 or (212) 986-5281.

* Winter Park (Colorado) Ski Resort: As many as 11,500 beginning skiers with some form of disability have participated in Winter Park's 13-year-old program, considered the largest in the world. Three two-hour lessons a day, equipment loans and lift tickets free to applicants. Instructors include therapeutic specialists from around the country working for academic credit, plus a large full-time staff. For information: Handicap Office, Winter Park Recreation Association, Box 36, Winter Park, Colo. 80482 or (303) 726-5514, ext. 179.

* The National Handicapped Sports & Recreation Association: Nonprofit group providing winter sports opportunities for the disabled. Executive director Kirk Bauer, who lost a leg in Vietnam, is a skiing amputee and instructor. This year's program includes seven regional ski clinics, with the Northeast division's this week at Sunapee (N.H.) Ski Area and the next one scheduled for March 9-13 at the Snowqualimie Ski Area near Seattle. Also a series of regional races for a national championship. Instruction and adaptive equipment generally provided free. The local association holds occasional clinics at Ski Liberty, near Gettysburg. For information: NHSRA, Farragut Station, Box 33141, Washington, D.C. 20033 or 429-0595.