An unhappy milestone was passed this week when American newsman Terry Anderson began his fifth year of captivity in Lebanon.

The occasion has drawn new attention to Anderson and 14 other foreigners being held hostage in Lebanon - together with new sympathy for their plight. But that's no comfort to their families and friends. Nor is it any cure for the frustration Americans feel.At the same time, it's hard to know what else Washington can or should do except to keep following its present policy of being willing to talk to the kidnappers but offering no concessions.

Anderson is being singled out for attention simply because he has been held hostage in Lebanon longer than any of the 14 other Westerners - eight Americans, including Idaho native Jesse Jonathan Turner, three Britons, a Belgian, Irishman and an Italian.

Their plight is truly pitiable, since all indications are that the hostages are not only deprived of freedom but also held under barbaric conditions, chained and blindfolded.

But it would be folly to offer concessions for their release, since that would only encourage more hostages to be taken in pursuit of still more concessions. Besides, such concessions can backfire in other ways - as was demonstrated by the way Ronald Reagan got so badly burned by the abortive arms-for-hostages deal with Iran.

Moreover, the situation is complicated by the fact that the hostages are being held by different Moslem factions. Though all the factions are said to fall under the jurisdiction of an umbrella group called Hezbollah, it isn't clear that Hezbollah is able to exercise much control over them.

The most hope seems to be offered by reports that many Moslems are ashamed of what the hostage-takers have done, realizing that it damages the image of Islam in the eyes of the world.

Under the circumstances, Washington's most effective course is clear: Don't let the new headlines generated by the plight of the hostage pressure us into making concessions. But don't forget the hostages either. Quiet, traditional diplomacy still offers the best hope for their eventual release.