THE WASHINGTON area is rich in opportunities for bicyclists of all abilities and inclinations. The surrounding countryside, although harder to reach than in the past, has many miles of scenic roads. Inside the Beltway exists an extensive system of bike trails and routes. And finally, there is a very large and well organized network of local clubs, agencies and other organizations that cater to the Washington cyclist. WHERE TO RIDE? BIKE TRAILS

Local bike trails range from wide and well maintained to narrow, twisting, debris-strewn obstacle courses. Because they're in densely populated areas, the trails tend to be heavily used. On weekends some are dangerously congested with joggers, skaters, baby carriages, children and dogs. Use care.

THE MOUNT VERNON TRAIL runs from Memorial Bridge south along the Potomac River to Mount Vernon, almost 17 miles. The trail is well paved and maintained, although narrow in places. It has wonderful views of the river and is virtually flat. On weekends, it is one of the most heavily used bike trails in the country.

THE ROCK CREEK BIKE TRAIL runs from Memorial Bridge north into Montgomery County. At its southern end the trail joins up with the roads and trails around the Mall and East Potomac Park (a popular place for local hotshots to do laps). The trail in the District is generally narrow and somewhat twisting. It parallels Rock Creek and is very scenic. Stretches of Beach Drive are closed to auto traffic on weekends and are opened to bikes and pedestrians. The trail is also crowded on weekends. Watch out for all the dogs running around loose.

IN VIRGINIA, the Washington and Old Dominion Bike Trail (known as the W&OD) runs from near Shirlington to Leesburg. It's a wide, well maintained path built on the old railroad right-of-way. The Custis Trail runs to the W&OD from Key Bridge in Rosslyn, while the Four Mile Run trail connects it with the Mount Vernon Trail south of National Airport. The connections on the Four Mile Run trail are not well marked.

The WO&D is an example of what a bike trail should be. It is wide enough to allow for safe passing, has few blind turns and is well marked. Its minuses are too many at-grade street crossings and a lot of traffic in the more heavily populated areas. Contrast that with the MacArthur Boulevard bike trail in Maryland. It is covered with loose gravel, glass, grass clippings and parked cars. It also shows poor planning in the way it snakes across MacArthur Boulevard several times.

There are many other lesser known trails in the area. Local park and transportation agencies can give more information.ON THE ROAD

Washington is surrounded by beautiful countryside. To the north and west are mountains and hilly terrain. To the east and south are the piedmont and coastal plains. The terrain ranges from level to near-vertical.

There are several things to look out for, including aggressive dogs and surly motorists. Both exist in substantial numbers and can get a rider killed or seriously injured. Always wear a helmet!

One nearby area that cyclists treasure is the USDA's National Agricultural Research Center in Beltsville. It's a ride through the country just outside the Beltway. Just about any evening of the week will find scores of riders out training or just enjoying.

Southern Maryland's relatively flat, relatively rural and offers easy terrain and good roads. Anne Arundel county is becoming built up, though, especially around Annapolis.

Northern Montgomery County is rolling to hilly. Southern Montgomery is by and large too densely populated for enjoyable riding. The areas around Dickerson, Poolesville, Barnsville and Sugarloaf Mountain have long been popular with local riders. North of Gaithersburg, Damascus is the gateway to Carroll, Howard and eastern Frederick counties. North of Olney are reservoirs, rivers and farms. Ellicott City in Howard County is a popular destination.

The outlying counties (Howard, Frederick, Carroll and Anne Arundel) are less populous. With the exception of Anne Arundel, they are fairly hilly. Although it is not difficult to stay in the valleys between the ridges, some climbs must be expected. Western Frederick County is very hilly, including as it does the Cactoctin Mountains. All of these counties have many lovely small towns.

Northern Virginia, like Maryland, has experienced rapid growth, which makes it harder to get to the country (or at least a longer drive). However, many excellent areas for riding remain.

Loudoun County is still largely rural and has some gorgeous farms and estates to gawk at while pedaling by. The area around Middleburg is justly famous for its horse farms and scenery. It is somewhat hilly for novice riders, but worth the effort. Purcellville, Waterford and Lovettsville in northern Loudoun are also worth visiting.

Farther south, western Fairfax county has some nice riding left around Dulles Airport, but development is coming on fast. The Lorton-Occoquan area is nice for cycling also. Prince William County still retains much of its rural flavor, although road traffic is increasing. Still, the Nokesville and Quantico areas remain local favorites, with generally good roads and rolling terrain.

The adventurous can travel to Fauquier and Stafford counties, which are still rural. The truly hard-core can go to Front Royal and ride Skyline Drive. MAPS AND PUBLICATIONS

Local riders are fortunate in that several wonderful reference guides are devoted solely to local riding. Most notable is the Cycleways series by local riders Gail and Charles Helfer. Available from local bookstores and bicycle shops, the three Cycleways books cover riding in Montgomery and Howard Counties, in Northern Virginia, and in Central and Southern Maryland, respectively. The books consist of a number of rides ranging from 20 to 50 or more miles, each with several variations. Each ride has a general description of location, points of interest and terrain, as well as cautions. The books provide a map of the route and a "cue sheet" giving directions by distance. Each is easily photocopied to bring along.

Also blessing the local scene is the Greater Washington Area Bicycle Atlas, published jointly by the Washington Area Bicyclist Association and the Potomac Area Council of the American Youth Hostels. Like Cycleways, it provides descriptions, cues and maps for its routes, which include several longer, multi-day tours. It, too, is available from bookstores and bike shops.

Both books also have sections on maps, guides and clubs.

New on the scene is a bi-monthly magazine devoted to local cycling news. Called Spokes, it is available through bike shops, magazine and book stores and fitness establishments.

Local and state governments' transportation, planning, parks and tourism departments usually have map programs. Also check with the National Park Service.

OFF-ROAD RIDING

Off-road bikes, mountain bikes, all-terrain bikes (ATBs), whatever you call them, they're here to stay. It can also be confusing to find out where to ride them legally. Some people confuse them with dirt bikes (motorcycles) and some hikers are determined to keep their trails to themselves. Regulations are often up to individual park managers, so check before you go.

One trail that was seemingly made for ATBs is the C&O Canal. Wide, flat and in reasonably good condition considering Mother Nature's recent ravages, it is the perfect place for a fat-tire bike. Fenders may be in order during the wet season.

CLUBS AND ORGANIZATIONS

D.C. has a plethora of clubs and groups devoted to cycling. The Potomac Pedalers Touring Club is the largest in the country with several thousand members and a full schedule of rides and activities year-round. There are several other smaller but no less active clubs in the area.

There are also racing clubs that field teams for competition and stage their own races, the most notable being the National Capital Velo Club's annual National Capital Open, which is run around the Ellipse each spring and features some of the finest riders in the country.

There is also at least one organization, the Urban Nomads, devoted to all-terrain bikes.TOURING CLUBS

POTOMAC PEDALERS -- P.O. Box 23601 L'Enfant Plaza Station, Washington DC 20026. RESTON BICYCLE CLUB -- P.O. Box 3389 Reston VA 22090. OXON HILL BICYCLE AND TRAIL CLUB -- Box 18081 Oxon Hill MD 20745. POTOMAC AREA COUNCIL/AMERICAN YOUTH HOSTELS -- 1017 K St. NW. RACING CLUBS

WHOLE WHEEL VELO CLUB -- c/o The Bicycle Exchange, 9446 Main St. Fairfax VA 22031.

NATIONAL CAPITAL VELO CLUB -- 4012 Wexford Dr. Kensington MD 20895; 946-2985

COLLEGE PARK BICYCLE CLUB -- P.O. Box 208 College Park MD 20740.

CENTURY BICYCLE RACING CLUB -- 940 Bonifant St., Silver Spring MD 20910; 585-5868

URBAN NOMADS -- all-terrain bicyle association. P.O. Box 5627, Arlington VA 22205. OTHER ORGANIZATIONS

WASHINGTON AREA BICYCLE ASSOCIATION -- Education and advocacy. 530 Seventh St. SE, Washington DC 20003.

BIKE LINE -- Call HEY-BIKE for upcoming events. P.O. Box 468 College Park MD 20740.

METRO BIKE-ON-RAIL allows cyclists to bring their bikes on Metro trains on weekends and holidays and after 7 p.m. weekdays. A real boon to those trying to reach the boonies without a car. Call 962-1116 for information. For information on bike-locker rentals at Metro stations call 962-1327. HELP FOR COMMUTERS

The Montgomery County Department of Transportation has a "Bicycling Routes in Lower Montgomery County" map showing bikeways and suitable unsigned roads for riding. Available for $1.50 at county libraries or write to the DOT's Planning Office (include check for $1.50), Rockville MD 20852.

"Getting Around Washington by Bicycle," is $3 from the Office of Documents, Room 19 in the District Building. Also, the D.C. Department of Transportation's Bicycle Program, 415 12th St. NW, Washington DC 20004 (939-8016), has information and a brochure for those interested in D.C. cycling opportunities.

"Bicycle Routes in the Washington Area," from the Metropolitan Washington Council of Governments, is available at local bike shops.

Get a free Bikeway map of Arlington and I-66/Custis Bike Trail by writing to Public Works Planning, Room 221, 1400 N. Court House Road, Arlington VA 22201.