Sometimes a cast is better than a show deserves. In the case of "42nd Street," which opened its third engagement in Washington at the National Thursday night, the singers and dancers work so hard to overcome the essential cynicism of the production that they just about persuade you to throw off your troubles and chase all the blues away.

"42nd Street" has the feel of a revival, but actually it was created in 1980 from the remains of a 1933 movie starring Dick Powell and Ruby Keeler that had four songs and some tap dancing. Now it has 15 songs, all pirated from other '30s movies, done up beautifully slick and snappy for the 1980s, and enough tap dancing to scare off an advancing army.

The dancing is still spectacular, with credit due to director-choreographer Gower Champion, who died the day the show opened in New York. The dancers' art, when the chorus line is at full throttle, blessedly strips down the often foolish gawdiness of the rest. At times the panoply of costumes and sets moving in and on from all directions is like a diet of chocolate -- more riches than one can stomach.

The rest of the time "42nd Street's" job is to breathe life into old cliche's without being campy. The saga of star-struck Peggy Sawyer, who comes to New York to get into show business, and is hired and fired from the chorus line and named the star of the show in the same day, may have been charmingly naive in 1933. In the 1980s, it is just a vehicle for some great songs, like "Lullaby of Broadway," "We're in the Money" and the title number.

The plot burbles along predictably, with plenty of breaks for production numbers (10, to be exact). And should the action flag, even briefly, well . . . bring on the girls! Drape them in brief costumes on glittering sets, pulchritude on display like pandas in the zoo.

Make no mistake, this show was designed with the expense account crowd in mind. After it opened in New York to good reviews, producer David Merrick promptly raised the top ticket to $40. At over $2 million, it was at the time the most expensive musical ever produced, and Merrick has handily recouped his investment. More power to him.

This production is virtually the same as the one that reopened the National just over a year ago. If anything, the dancing is better. Barry Nelson still cannot sing his way out of a paper bag and doesn't seem to care -- nor does the audience. He talks as if his mouth is stapled in both corners and walks like someone who's left the hanger in his jacket, but has a boyish yet aged appeal, if such a thing is possible. Dolores Gray, artfully draped in carefully designed costumes, seems more relaxed than last year, and she wraps her throaty voice around classics such as "You're Getting to Be a Habit With Me" and "I Know Now" with authoritative charm.

If Gail Benedict weren't such a terrific dancer and singer, her Pollyannaish Peggy Sawyer would verge on the saccharine. I know she's supposed to be a wide-eyed innocent, but Benedict seems to be grinning even when she's collapsed in a dead faint. James Mellon as the self-important young tenor is impressive both singing and dancing, but seems to have skim milk in his veins. Sandra Yarish's Annie, the slutty chorus girl who pulls it all together, is a delight, and Denise Lor gives the brassy Maggie a judicious degree of oomph.

42nd Street, produced by David Merrick, music by Harry Warren, lyrics by Al Dubin, book by Michael Stewart and Mark Bramble, based on the novel by Bradford Ropes, directed by Lucia Victor from the original by Gower Champion, choreography by Gower Champion reproduced by Karin Baker and Randy Skinner, scenery by Robin Wagner, costumes by Theoni V. Aldredge, lighting by Tharon Musser. With Dolores Gray, Barry Nelson, Gail Benedict, James Mellon, Denise Lor, Barry Preston, J. Frank Lucas, Randy Phillips, Don Potter, Lew Resseguie, Sandra Yarish. At the National Theatre through May 5.