'Frontline' documentary; 'Vietnam Memorial' raises troubling national memories

The American presence in Vietnam may be over, but Vietnam remains in the American conscience. The significance of US participation in the Vietnam war is still being defined as the United States tries in retrospect to understand the reality of intent and effect.

But while America grapples with its own ambivalence, belatedly hailing its warriors, reexamining its motivations and procedures, a filmmaker has come along with one of the most powerful, moving, and truthful statements about that war yet devised.

Vietnam Memorial (PBS, Monday, 8-9 p.m., check local listings)m is a wrenching film that masquerades as the story of last year's dedication of the Vietnam Memorial in Washington. But it is really the story of all those who participated - those who died, those who returned, those who waited, those who still wait. Part of the ''Frontline'' series of weekly documentaries, ''Vietnam Memorial'' represents the pinnacle of achievement of that sometimes uneven program, which must depend upon the creativity of individual filmmakers. Using a kind of modified cinema veritem format, filmmakers Steven York and Foster Wiley have emerged with a triumph of understatement, an elegiacal testimony that as a nation the US is strong enough to delve deeply into its defeats as well as triumphs.

''Memorial'' is the story of anguished doubts, bitter pride, self-conscious righteousness, determination to straighten things out. In its own tenderly raucous way it is also a tale of love and duty. Ironically, in the midst of war reunions and the ensuing reminiscences, one veteran exclaims: ''There's never been so much love in one place at one time in history.''

Find the strength, on a day set aside to remember those who gave their lives, to watch this touching, narrationless film. It wanders in seemingly aimless manner through the streets and malls of Washington, eavesdropping on debates, dedications, entertainments, private grief, and public displays of a variety of patriotisms. At times it will be painful - there are poignant moments when the alleged victims of Agent Orange voice their impatience with the Veterans Administration and when lines of wheelchairs ''march'' through the streets. And there is some rough but realistic street and trench language.

Edited with contrapuntal skill, the film causes certain themes to leap off the screen and sound track. ''The shame is in the eyes of the beholder,'' one voice shouts as another voice repeats over and over: ''Spread the word - we didn't lose. Spread the word. . . .'' Again and again, almost subliminally, a sign appears on screen. It represents a kind of recurring theme: ''No More Vietnams.''

But the most unforgettable moments come now and then as the fingers of relatives and survivors search the black granite slabs of the memorial for the names of their loved ones, find the engraved names, linger over them as they touch the names in silent tribute and memory.

''Vietnam Memorial,'' the film, is almost as effective a memorial as the Vietnam Memorial monument itself.