A shower of confetti, miles of red, white and blue streamers and two high school marching bands hailed the opening yesterday of 40 new shops in the National Press Building complex.

About 1,000 people were drawn to the midday ceremony at 14th and F streets NW, where Mayor Marion Barry proclaimed, "Downtown is coming alive . . . !"

"Let's hear it for The Shops! Let's hear it for Washington, D.C.!" the mayor yelled to the spirited crowd, which had been revved up by the Cardozo and Dunbar high school bands.

The hoopla was in celebration of more than the opening of 40 businesses.

Just five years ago downtown Washington, like the center of many large cities, was dying, as retailers and shoppers rushed to the convenience of suburban malls. The 1968 civil disturbances and the sluggish construction of Metro persuaded other retailers to leave the District.

But the tide has turned, developers and city officials say, thanks to the coming of Metro, construction of the Washington Convention Center and other developments. Mathias J. DeVito, chairman and president of the Rouse Co., developer of the complex, told the crowd: "There is no longer any doubt about the retail comeback of downtown Washington."

The mayor offered as proof " . . . the Pavillion, the Marriott . . . . Right across the street . . . the Willard Hotel . . . ," where construction workers stopped to watch the ceremony.

The 40 new stores, including August Max, Brooks Fashions and Record Town, are the second phase in a year-old Rouse Co. complex officially called The Shops at National Place and National Press Building, but casually called "The Shops" by downtowners.

The entire mall, which now has 85 stores, occupies the block bounded by Pennsylvania Avenue and F, 13th and 14th streets NW. It also includes the National Theatre, 418,000 square feet of office space, the 774-room J.W. Marriott Hotel, and a 450-space underground parking garage.

The new shops are in the extensively remodeled National Press Building, which will be rededicated next month. The building features 2 1/2 levels of shopping and a 15-story atrium with glass elevators that come to rest at reflecting pools on the first floor. Parking is underground and offices are overhead.

Outside, construction is everywhere. Across the street on the northeast corner of 14th and Pennsylvania, the Willard Hotel is being renovated and will one day include an office building and some retail shops.

In the next block up 14th Street, a $10 million renovation is under way at Garfinckel's, part of a project called Metropolitan Square, which when completed will cover an entire block bounded by 14th and 15th Streets and F and G streets.

Phase I of Metropolitan Square has already been completed and includes the Old Ebbitt Grill and retail and food shops. On the south side of F Street, between 12th and 13th streets, former site of a Morton's store, Columbia Square is planned -- offering more shops, offices and stores. Later this year the new Hecht's department store, on G Street between 12th and 13th streets, will be finished, a part of the Metro Center complex. The Metro Center project also will include a hotel, offices and more retail shops.

The list of planned downtown projects is long, including: A hotel in Chinatown, a Hyatt Regency hotel near the convention center and reconstruction of the Bond Building -- more office and retail space -- at the southwest corner of 14th and New York Avenue.

"Washington is vibrant," Fred Greene, director for the Office of Planning, said yesterday, using the same excited tone of boosterism as the mayor.

What is attracting retailers now?

"Success," said John Hayden, retail specialist for the Oliver Carr Co., pointing to The Pavillion and The Shops.

"You have many markets in downtown that you don't have elsewhere," said Garry Curtis, manager of the retail bureau of the Greater Washington Board of Trade. "There's the convention center now, the proximity of the Smithsonian means tourists . . . and a daylong influx of workers."

"It has been in the last five years, since the Metro complex was completed and enough lines built to the rest of the city," Curtis said.

"And downtown has turned around."