WASHINGTON -- If you have a few choice words for the Internal Revenue Service when your tax return is audited, your IRS officer could have a few choice words for you -- and toss you into a secret listing of "Potentially Dangerous Taxpayers."

In fact, the names of more than 8,800 taxpayers have been placed in the so-called PDT File, designed to track potential threats to the IRS.

Some, like the Bethesda accountant who pleaded guilty in Baltimore last July to conspiring to murder an IRS auditor, may have assaulted or tried to assault IRS agents. Some may have threatened or harassed agents. Others may be members of tax groups advocating violence against the agency.

Although the list initially was set up for internal IRS use, it is being distributed to state and local law-enforcement agencies, a practice that concerns civil liberties groups, since most of those on the list are neither convicted criminals nor defendants in criminal cases.

The file contains the names, addresses and case histories of individuals who have made threats, assaulted, harassed or otherwise attempted "to interfere with the administration of the internal revenue laws," according to Treasury Department rules published in 1984.

Taxpayers on the list have asterisks placed next to their names in their general IRS files. If an IRS agent sees the asterisk and wants information about the incident that landed the taxpayer on the list, he must contact headquarters.

IRS officials said the listing was developed in the 1980s to deal with an increase in harassment, threats and actual assaults against IRS employees -- incidents ranging from the Maryland murder-conspiracy case to last week's launching of 10 pipe bombs at an IRS center in Fresno, Calif. More than 730 incidents of varying severity were reported last year.

Currently, 8,838 taxpayers have been designated as "potentially dangerous," including 171 in the Baltimore-Washington IRS District, according to IRS officials.

The existence of the file has not been common knowledge and its contents are secret -- at least to the public and those who want to know if their names are on the list.

For example, the Privacy and Technology Division of the American Civil Liberties Union, which monitors this kind of operation, was not aware of the PDT File until told about it by a reporter.

"The serious questions this raises are both of privacy, in that people's names are in a file which could have very negative consequences, and of constitutionality, when they haven't committed a crime and they're not even wanted for committing a crime," said Janlori Goldman, who heads the ACLU's privacy and technology division.

Although IRS officials say the PDT file is used internally as a warning system alerting examiners and revenue officers to taxpayers prone to acts of violence, it has actually been made available through a centralized listing to several states -- including Arkansas, Florida, Georgia, Louisiana, Indiana, Illinois, Montana, South Carolina and South Dakota, according to an IRS list of databases shared with state agencies.

According to John Schnellmann, public affairs officer at the IRS office in Washington, any state can receive information on PDTs, subject to negotiations with the IRS central office.

But, if a private citizen wants to find out if he or she is on the list, the IRS will most likely withhold that information, especially if the citizen is, in fact, on it.

"Our feeling is that if you know you're a PDT, you're liable to be so hostile that you are going to go out and do violence to an individual," said IRS Internal Security Division Director Douglas C. Crouch. "Before, you may have threatened him [the IRS

agent]; now, you're on his computer database -- and now you're really upset."

Crouch emphasized that citizens are not labeled Potentially Dangerous Taxpayers on a whim. He said there is a careful

screening process that starts with the complaining IRS employee. It generally includes a return visit to the taxpayer in question and moves through district-level coordinator to the regional coordinator.

"We try very hard to make sure that if you're designated a PDT, that you truly deserve that designation," said Crouch, "because I don't think any of us want to wind up on some database some place having that kind of code next to our names."

When asked if the Justice Department or any other computer database cross-references the PDT list, Crouch said the information generally remains within the agency because "that PDT information is associated with you as a taxpayer -- that tax return information remains in the IRS. We do not share that with anybody."

Crouch later admitted, "There are certain times when we're allowed to share -- the Department of Justice can write in to get it. But, for the most part, we guard that information very cautiously."

It is the sharing of such private designations that alarmed the American Civil Liberties Union, which in the past has opposed the drafting of lists of suspects, citing the potential for abuse.

"You don't have to be a genius to see that if the IRS claims the list is private and for their own use -- but they're making it available to state law-enforcement agencies -- that list is out of their control," said the ACLU's Goldman. "It could be used as a basis to increase surveillance, initiate surveillance on somebody."

Goldman said the only similar file of potentially dangerous suspects is the FBI's file of individuals who might harm the president or vice president.

"But that has under 20 names in it," she said. "And it is the only file of its kind that I'm aware of that has a list that is available to law enforcement, of people who have not committed a crime, who are not wanted for committing a crime, who have not been convicted of a crime, but who might commit a crime."

IRS officials said PDT designation is not permanent. If no incidents are reported involving the taxpayer after five years, the individual may be purged from the file.

Appeals by individuals who feel they have been wrongly accused occur rarely, according to Crouch, who said a taxpayer would have to prove "to our satisfaction" that he or she was not potentially dangerous. He could not recall any such attempt.

While the PDT file is not the only way the agency tracks troublesome taxpayers, its availability to other law-enforcement agencies can cause the most problems, according to Paul J. DesFosses, who worked as an IRS agent for 20 years.

Now retired, DesFosses is president of the Washington-based National Coalition of IRS Whistleblowers, a watchdog group of current and former IRS employees.

"There's also a list just of tax protesters -- and that includes hundreds of thousands of people active in churches and other groups that are considered to operate actively against the IRS. If you're on that list, you will be scrutinized very carefully for the next several years," said DesFosses.

"But, if you're on the PDT list, there's a good chance you'll be shot one day," he said. "Then you're really a target. And if you're stopped for speeding or something, the police will cross-check your record and call for a backup. Then they'll come at you with guns."

It is difficult to determine what state agencies have actually done with the information. For example, state police and treasury officials in Louisiana, Georgia, Montana and Illinois said they were unaware of the existence of the PDT File, even though IRS records show they had received copies.

For his part, Crouch said IRS agents often have something to fear, and the PDT File is a good defense. "The murder-for-hire case in Baltimore -- now that started out as a routine audit, and two people ended up in prison," he said.

The case involved the discovery of a plot to kill Stewart Connard, a Baltimore District revenue agent who was delving into the finances of Bethesda accountant Joel D. Davis in 1980.

Prosecutors finally wrapped up the case in July, after Davis, who had fled to Israel, was extradited and pleaded guilty to hiring career criminal Douglas L. Sanders to murder the agent. Both conspirators are serving prison terms.

But the list was begun more as a reaction to the increased national tax-protest activity in the 1980s than to such rare incidents.

Particular attention was paid to sabotage campaigns by groups like the West Coast-based Posse Comitatus, the New York Patriot Society for Individual Liberty and the mysterious California-based Up the IRS Inc., which last year claimed responsibility for the 1990 attempted bombings of IRS office buildings in Los Angeles.

The IRS internal security division has determined that last week's pipe-bombing in Fresno bears a marked similarity to the Los Angeles activity.