The job of the professional, full-time State Department courier -- unlike the occasional lark of the free-lance commercial courier -- is apt to be more arduous, even dangerous.

In the C Street lobby of the Department of State, a small plaque carries the names of five men killed while serving as diplomatic couriers. Below their names is this inscription by Albert J. Verrier, current chief of the U.S. Diplomatic Courier Service: "For it must be remembered that Diplomatic Couriers, through continuous travel and the singular nature of their duties, are constantly in harm's way."

The 74 members of State's Diplomatic Courier Service (63 "travelers," nine field supervisors and two Washington supervisors) fly approximately 14 million miles a year, carrying sealed diplomatic pouches from Washington, Bangkok and Frankfurt to government offices in 135 cities and countries around the world.

About 700 men and women have served as diplomatic couriers. While numerous couriers have been exposed to hostile fire (including during the Soviet invasion of Afghanistan), the five fatalities have resulted from air crashes.

But despite potential dangers associated with the job, applicants far outnumber vacancies in the service, which is considered prestigious. The one to three courier slots that open each year are filled solely from the ranks of the Foreign Service.

"A basic requirement," says Verrier, 54, who entered the Courier Service in 1955, "is that applicants have served at least three years as Foreign Service employes, although most have eight to 10 years' service." The average age of couriers is in the mid-forties. They receive the same pay as other Foreign Service employes of equal grade.

Tours in the three courier offices run anywhere from two to six years and, says Verrier, "involve a mix of the good and bad trips."

Couriers travel on both military and commercial aircraft, with "the great majority on commercial carriers." Contrary to any romantic notions the public may have, diplomatic couriers look no different from any other commercial travelers. There is no telltale briefcase handcuffed to the courier's wrist; the diplomatic pouches, which look like large, canvas duffel bags, ride with the other luggage, in the cargo hold.