Laura Bush has made her choice. Ending weeks of speculation on Seventh Avenue about what she would wear on Inauguration Day, Jan. 20, Mrs. Bush said Monday that Oscar de la Renta would design her inaugural ball gown, a dress that for a time at least will be the most scrutinized in the country.

The silver-blue tulle gown, embroidered with bugle beads and outlined in Austrian crystals, is the stately if conventional centerpiece in a wardrobe Mrs. Bush will wear during four days of festivities in Washington, including 10 balls, candlelight dinners, a parade and fireworks.

In addition to Mr. de la Renta, a longtime couturier to the fashionable elite, designers for Mrs. Bush's wardrobe include Carolina Herrera, who fills a similar niche, and Peggy Jennings, a little-known designer who has been quietly wardrobing Mrs. Bush from her apartment at the Waldorf Towers in Manhattan for two years.

The president's daughters, Jenna and Barbara, will be dressed by Badgley Mischka, Lela Rose, Derek Lam and Mr. de la Renta for the inaugural festivities.

The first lady's wardrobe is sure to be studied for clues about her evolving personal style and even for hints about the overall tone of the White House in the next four years. "The first lady is certainly a reflection as to the man holding the office," Mr. de la Renta said. He was reluctant to ascribe special significance to Mrs. Bush's sartorial choices, which are more glamorous than anything the White House has seen since the Reagan years.

But another observer, Catherine Allgor, a historian of first lady style, suggested that in anointing Mr. de la Renta and Mrs. Herrera, mainstays of taste among wealthy women, Mrs. Bush appears to be displaying a growing awareness that "her power is entrenched." "She has gone from being just folks to being a bit imperial, assuming a bit more of a queenly role," said Ms. Allgor, the author of "Parlor Politics: In Which the Ladies of Washington Help Build a City and a Government" (University Press of Virginia, 2002).