examine all the evidence and follow all the facts, wherever they lead,'' Mr. Bush said at the bill-signing ceremony, with Mr. Kissinger at his side. ''We must uncover every detail and learn every lesson of September the 11th.''

White House officials said Mr. Kissinger was an attractive choice because while he has extensive experience, he has been out of government long enough that he has few ties to the people and agencies whose actions he would be examining.

Advisers to the White House said the administration believed that Mr. Kissinger had sufficient prestige that he could be independent of Mr. Bush, but at the same time was someone Mr. Bush and his staff could be comfortable with.

The appointment surprised relatives of the Sept. 11 victims, who had been the primaryforce behind the legislation and who had been consulting with the administration and Congressional leaders about who would be on the commission.

It also raised questions among Democrats about whether Mr. Kissinger, who served in the Nixon administration and in every later Republican administration, would pursue an aggressive investigation that would delve into delicate topics like the role of Saudi Arabia and risk findings that could prove politically explosive for Mr. Bush.

In particular, they pointed to Mr. Kissinger's record of operating in secrecy and accusations about his involvement in incidents like the 1973 coup in Chile that toppled the Socialist government of Dr. Salvador Allende.

But some Democrats said they were confident that Mr. Kissinger's stature and visibility, combined with the appointment of Mr. Mitchell and promises by the victims'