In a survey sent to 1,500 libraries last fall by the Library Research Center at the University of Illinois, the staffs at 219 libraries said they had cooperated with law enforcement requests for information about patrons; staffs at 225 libraries said they had not.

Ms. Turner said the authorities had made no inquiries about patrons in Santa Cruz. But the librarians here and the library board, which sets policies for the 10 branches, felt strongly about the matter nonetheless. Last month, Santa Cruz became one of the first library systems in the country to post warning signs about the Patriot Act at all of its checkout counters.

Today, the libraries went further and began distributing a handout to visitors that outlines objections to the enhanced F.B.I. powers and explains that the libraries were reviewing all records ''to make sure that we really need every piece of data'' about borrowers and Internet users.

Maurice J. Freedman, president of the American Library Association and director of the library system in Westchester, N.Y., said only a handful of libraries had posted signs or handed out literature about the Patriot Act. Warning signs are posted in the computer room at a library in Killington, Vt., and the library board in Skokie, Ill., recently voted to post signs, Mr. Freedman said.

Many other libraries, he said, including those in Westchester, decided that warnings might unnecessarily alarm patrons.

''There are people, especially older people who lived through the McCarthy era, who might be intimidated by this,'' he said. ''As of right now, the odds are very great that there will be no search made of a person's records at public libraries, so I don't want to scare people away.''

At the same time, though, thousands of libraries have joined the rush to destroy records.

A spokesman for the Justice Department said libraries were not breaking the law by destroying records, even at a faster pace. The spokesman, Mark Corallo, said it would be illegal only if a library destroyed records that had been subpoenaed by the F.B.I.