"Lost in Yonkers" is a valuable addition to that genre of wartime plays that take place in bunkers or trenches.

Though the play is set in 1942 in a comfortable apartment in Yonkers, it has an air of constant tension not unlike Verdun. In some of Neil Simon's plays he creates an air of specious hysteria just to keep the laughs coming. Here that is unnecessary. The laughs all grow out of the situation.A widower father who owes a huge amount of money gets a job as a traveling salesman and is forced to leave his two young sons with his mother, a glacial woman who has never shown affection to anyone. At first, the play, which abounds in grotesque characters, seems Dickensian in its understanding of childhood as a time of terror and immense strangeness.

Then Simon's real concerns become clearer. In many of his plays he has exploited Jewish characters and situations for comic effect. In the last few years he has begun to take Jewish values seriously, and in "Lost In Yonkers," he tackles the subject with insight and power.

The play focuses on an elderly German-Jewish woman, the matriarch of a family that includes a retarded, pathetically affectionate daughter; a gangster son; a daughter whose breathing goes haywire whenever she visits the dowager, and a son whose spirit the mother has broken, but who, in the course of the play, finds a new strength.

At first, the woman seems more German than Jewish. She came of age in Berlin before World War I and her iron will, her punctiliousness make her seem more a disciple of Bismarck and Clausewitz than a daughter of Zion.

And yet, when she finally - almost contemptuously - speaks in her own defense, we see that what has motivated her has been an obsession with survival.

Moreover, though she does not luxuriate in self-sacrifice in the way that has inspired countless Jewish mother jokes, we eventually see, to our surprise, that she is profoundly capable of it.

Survival and self-sacrifice have traditionally been Jewish concerns. By addressing them without the usual Jewish sterotypes or cozy humor, Simon has written an unusually tough play.

It is also a wonderfully theatrical one. Gene Saks has directed the play with an intensity and imagination that mine its riches splendidly.

As the mother, Irene Worth assumes the dimensions of a prehistoric monster, her features already rigidified in an ice age of her own creation. She lugs herself around as if she were dragging chains: She is indeed encumbered by a sacrifice she made years ago, a sacrifice she has confided in no one.

Mercedes Ruehl, who made such a sexy impression in "Other People's Money," is extraordinarily moving as the gangly, slightly goofy, poignantly generous daughter, particularly in the second act when she makes clear her own understanding of her plight.

Kevin Spacey plays the gangster with a mesmerizing finesse that only accentuates the menace he represents.

Jamie Marsh, as the older of the two boys, has a face with a remarkable capacity to register varying degrees of horror, all of which have comic impact. As the younger boy, Danny Gerard gives a wonderfully bravura performance. The wrinkled brow of Mark Blum, who plays their father, is as accurate an index of potential ulcers as any hospital chart. Lauren Klein brings great warmth to the role of the aunt with the erratic larynx.

Santo Loquasto sets the tone of the play with his Hopper-like scrim suggesting nostalgia and dislocation. He conveys Simon's darkly comic mood in the plainly furnished apartment and the extroverted costumes.

"Lost In Yonkers" is one of Simon's most impressive and funniest plays.

- LOST IN YONKERS. By Neil Simon. With Irene Worth, Mercedes Ruehl, Kevin Spacey, Jamie Marsh, Danny Gerard, Lauren Klein and Mark Blum. Sets and costumes by Santo Loquasto. Lighting by Tharon Musser. Directed by Gene Saks. At the Richard Rodgers theater in New York. (212) 221-1211 or Ticketron at (212) 246-0102. Good seating available.