The suit, filed in U.S. District Court in San Francisco, seeks to require the Bush administration to reveal how many names are on the lists, how names are added and removed and how often they have been used to identify the wrong person.

"Secret government lists do not allow the public to provide any oversight or comment into our government's activities, nor does secrecy make us any safer," said Jayashri Srikantiah, an American Civil Liberties Union lawyer taking part in the suit.

The ACLU said it sought the same information last December under the Freedom of Information Act, but the FBI replied that it had no such documents, and the Transportation Security Administration never replied.

Another question posed by the suit was whether the government is targeting political activists like Rebecca Gordon and Jan Adams.

The two women, who help publish the anti-war newspaper War Times, were detained briefly at San Francisco International Airport last August after their names showed up on a no-fly list at the American Trans Air counter. They were allowed to board their flight to Boston when officers didn't find their names on an "FBI list," according to police reports, but their bags were subjected to additional searches.

"Does someone in some government agency believe that our opposition to the current war policy means we are likely to commit terrorist acts?" Gordon and Adams asked. About 20 activists in Milwaukee asked similar questions a year ago after they were stopped at an airline terminal and missed their flight to a political gathering in Washington, D.C.

The government has provided little information about the data it has supplied to airlines since the Sept. 11, 2001, terrorist attacks.

But Heather Rosenker, spokeswoman for the Transportation Security Administration, denied Tuesday that anyone was on the government "watch lists" because of political affiliation or beliefs.

"The objective is to find terrorists and people affiliated with terrorists, " Rosenker said.

She acknowledged technical problems with computer links between airline databases and two lists compiled by her agency: the "no-fly" list of suspected terrorists and a list of "selectees," deemed less of a threat, who are subjected to added searches of their persons or luggage.

Evidence of those technical problems was provided by the ACLU, which released a summary from SFO of 339 people stopped at the airport between September 2001 and last month because they showed up on an airline's list. Police were summoned in virtually every case, but all but a handful were listed as cleared or dropped. It wasn't clear from the report what the outcome was in those few cases.

Adams, War Times' national distribution manager and co-publisher, said she had learned she had been detained and questioned because the actual no-fly list includes a J. Adams. Numerous similar incidents have been reported elsewhere.