PARIS (AP) _ One hundred and ninety-nine years ago, the Marquis de la Fayette gave the key to the Bastille to President George Washington. On Thursday, the Americans gave it back. Well, for a week anyway.

The Bastille was the central Paris prison stormed by the populace on July 14, 1789. That action became the symbol of the French Revolution.

The Bastille later was destroyed. But the marquis, who served as a general under Washington during the American Revolution, made a gift of the key as ''a tribute, which I owe as a son to my adopted father, as an aide de camp to my general, as a missionary of liberty to its patriarch.''

The key has hung in the central corridor of Washington's Virginia home, Mount Vernon, since the end of his presidency.

The key was presented to President Francois Mitterrand on nine-day loan by Eugenia Seamans, regent of the Mount Vernon Ladies' Association, a non-profit organization that has owned and operated Mount Vernon since 1858.

The large iron key will be displayed through July 22 at the new Paris Opera on the Place de la Bastille in central Paris, next to where the prison once stood, as part of France's bicentennial celebrations.

The very brief ceremony was held at the Elysee Palace immediately after the 40-minute meeting between Mitterrand and President Bush, here for the bicentennial festivities and to attend the summit of the seven major industrial democracies.

As Bush looked on, Mrs. Seaman told the French president it had hung in the central hall of Mount Vernon since 1797.

''Now it's again in Paris,'' she said, handing transparent box containing the key to a beaming Mitterrand.

As photographers and cameraman recorded the event, Mitterrand shook hands with Bush and said: ''I thank the successors of Washington.''

The loan of the key was arranged through the American Embassy in Paris and the U.S. Information Agency.

By Aug. 1, the famous key is expected to be hanging back in the hallway of the Mount Vernon mansion.