A motorcycle messenger was called for a pickup at Bristol Meyers to deliver a medium-sized cube box to the Longworth Building on Capitol Hill.

The guard at the desk became suspicious and insisted on inspecting the package. The messenger radioed his base and the dispatcher said it was okay to open it.

The guard did, looked at a mess of wires in the box, jumped back and cleared the lobby, saying, "Stay away from it, it's a bomb."

The Capitol police bomb squad was called in. They took a slow, cautious look at the contents - a set of electric curlers.

The Navy Yard is about 2 1/2 miles from Washington's business district, a long distance for a delivery. Bikers who work on commission, lose money on a trip that far.

One messenger biked during the business day to the yard's main gate. The security policeman there was under orders to inspect packages carried by suspicious-looking characters.

As the guard opened the package, the biker's face reddened. He had spent 20 minutes risking life and limb through heavy traffic on Pennsylvania Avenue, around the Capitol and down New Jersey Avenue to hand over a stuffed bunny rabbit.

Another messenger went to a private home in Georgetown to pick up a delivery one morning. A woman wearing a nightgown came to the door and handed him a brown bag. On the trip downtown several items rattled around. Dutifully the messenger whipped up the elevator of the office building and dropped the package off at the appointed office at 10:30. But before surrendering the paper bag, the messenger had peeked at the contents.

It contained shaving cream, razor, toothbrush and toothpaste. Thank you and goodbye. The Medium Is the Message

Taxis hate them; hospitals love them. They are ex-policemen, low students, PhDs, dropouts, actors, artists, models and, as one messenger put it, "Some are just blah, you know, gorillas."

They ride bicycles, motorcycles and scooters. Some are joggers. They grab sandwiches at carryouts.

Some work on salary, others on commission, averaging $150-$300 a week. There are about $1,000 of them, representing 30 to 40 delivery services. They move thousands of envelopes and packages around, averaging one package every five minutes of every working day.

They're the messengers of Washington, the city that can't get along without them.

They'll deliver anything. Birthday cakes, flowers, cookies, urine samples, prescriptions, X-rays, airline tickets, documents, photographs, car keys, paychecks, plants, stuffed panda bears. Most of the time they don't know what they've been carrying. A Danger Field

A car door opens suddenly and a biker is knocked down - out for several weeks with a broken collar bone.

A quick gust of winds knocks a young woman off her motorcycle, sending her across the street to land under a parked taxi.

The broken bones and bruises are many, and like the soldier after the battle, the messengers talk about them in a quiet proud way.

"Taxis are the worst," a bearded biker wants everyone in the recreation room at Central Delivery to know. Everyone there agrees.

Nelson Frick is a sort of folk hero to the messenger corps. Frick has an athletic build and wears his sandy hair short. Even on cold days he likes to wear colorful T-shirts and shorts. Frick survived the worst accident so far.

On the way to work a couple of years ago, Frick was riding down Massachusetts Avenue, keeping his lane, watching cars, pedestrians, obeying the rules of the road when he was hit by a car. He went over the hood of the car and crashed through the windshield.

Frick was unconscious for several days and suffered a broken leg and arm. He was laid up for six months, then worked as a bookkeeper with the delivery company's main office in Silver Spring.

When he was strong enough, despite his lame knee, Frick was back on his bike and he wouldn't give up his job for anything. "I love to ride a bike. I'd take this job a million to one against sitting in a stuffy office." Take the Money and Run

They take pride in getting the job delivered and sometimes call themselves "private mailmen."

David McComb, 26, has been running errands for the establishment for the past five years. One day McComb was told by the dispatcher that the envelope in is sack was very important.

The destination was an investment firm. On the way he peeked and found he was carrying three checks, each for $100,000.

Gail White picks up and delivers for Acuity Traffic, switching from her Yamaha Chappie motorcycle to her car, weather permitting. The 25-year-old former photographer's model was bored by her accounting courses at Benjamin Franklin University.

Acuity pays on percentage and gives the messengers 55 percent of every delivery, so White can make about $150 a week. "I never used to speed or park illegally, but money is an incentive," she said. The Ways of Will

Will Kreuzburg, at 6 feet 6 inches and 170 pounds is an imposing figure in his black company jacket, black skin-tight cycling tights, wool socks halfway up his calves, and white Adidas. A leather cycle-racing helmet sits atop of his long, straight black hair, and a well-trimmed moustache and beard hide most of his face.

Besides all the other equipment worn by cyclists , including cycle gloves, Kreuzberg has hitched a rear view mirror to the left side of his goggles. The mirror is about the size of a scrabble square and is attached to a wire extending out about an inch from his goggles.

Kreuzberg, 36, has had many jobs since his four years, in the Coast Guard. First it was 2 1/2 years at the University of Maryland, where he studied philosophy before switching to English at Prince Georges Community College. Then a brakeman's job on a railroad. He then moved on to foreman of the railroad yard and then became a cashier at Grand Union. Kreuzburg next took an inside job with the Wison Gill Electronics firm.

It was a 3,500-mile bike trip to four provinces in Canada and back that convinced Kreuzberg he was never again going to work indoors.

"I ride about 30 miles a day and make about 40 pickups and deliveries. My longest trip was to Alexandria and back," Kreuzburg said. On weekends he likes to take 60-mile trips with his girl friend. "I just live on my bike." Messenger Down Memory Lane

In 1948 the Yellow Cab Company of Montgomery County, looking for a way to keep the cabs moving when they lacked fares, contracted with a local chain for rush pickup and delivery.

The demand became so heavy that the back seats of two cabs were removed and they were converted into delivery vehicles.

Central now has 300 people on its payroll, with offices in Houston, Boston, Baltimore and Kansas City.

"Couriers, is a better word than messengers," according to John C. Steinberger, president of Speed Service Inc. "Anyone can deliver a message, these people perform a service." He founded Speed Service Couriers Inc., seven years ago, though he had drawn up the idea in the early '50s.

At that time he was involved with press work. In those days, before the advent of portable tape rigs and movable wirephoto machines, dispatches were in the hands of the press courier. The seconds counted when the courier was on his way back with film.

The late '50s brought refinements in the courier system.

In 1967, Steinberger started Speed Service Couriers with a motorcycle, an operations center and a two-way radio.

As still and motion picture cameras ranged farther and farther into the field, and with expanded deadlines and news shows, needs changed.

At first the news organizations added more couriers, motorcycles, and people. But it didn't work. Reporters, photographers and couriers were tripping over each other. The first practical application of the Speed Service System came with the inauguration of John F. Kennedy in 1961.

A heavy snowfall stopped traffic; even motorcycles had a rough time moving about.

There were a dozen balls to cover. Steinberger was then in charge of couriers for UPL and he solved the problem by having more men on the street, riding anything that could move.