Few Secrets Kept From Mail Marketers

IF you bought some slacks by phone this holiday season, rented a video, or donated money to a favorite political cause, chances are your name -- and a whole lot more -- is now on a marketing list.

Dialing a toll-free number may put your name and address on file -- even if you never identified yourself.

Direct marketers are using ever-more sophisticated techniques to learn about customers' buying habits. These firms say the information helps them tailor their sales' pitch to interested customers. But consumer groups charge that they are snooping too deeply into people's private lives.

''They can find out whether or not you bought software to psychoanalyze yourself, how many children you have, what type of car you have, how old it is, how long you have lived in your home, whether you have children or in-laws living at home, whether or not you wear dentures,'' explains Bob Bulmash, president of Private Citizen Inc., Naperville, Ill., which opposes junk mail and telephone solicitations.

The Direct Marketing Association, an industry trade group in New York, estimates that businesses have amassed 15,000 consumer lists with 2 billion names. R.L. Polk & Co. in Detroit and Metromail in Lombard, Ill., two of the largest consumer data companies in the United States, have files on about 90 percent of all US households.

In recent years, some companies have started gathering new lists of customers through automatic number identification (ANI), the commercial version of Caller ID. Call Processing Solutions in Parsippany, N.J., uses this technique to reduce the need for operators to write down addresses to send out free samples during special promotions.

''While we were in the process of greeting the caller, we would go out the backdoor to a data base of 85 million published telephone numbers and see if we could match that telephone number with a person's head of household name, street address, and city, state, and zip code,'' says company chairman Alan Adler. ''We would know within an eighth of a second.'' The number matches about 50 percent of the time, he says.

SOME companies add to their lists by using public records such as home deeds and car registrations. ''What we're trying to do is build the most comprehensive and relevant consumer information base for business,'' explains Ben Adams, R.L. Polk's senior vice president for database management.

Often this information can be obtained in seconds; for example, New York and 11 other states offer instantaneous computer access to individual driver records for a fee.

Not all Americans are impressed by this technological wizardry. ''I don't want them to use my phone for marketing or any other reason,'' says Dorothy Nettles, a Philadelphia retiree who learned recently that toll-free calls from her unlisted number can be traced back to her.

Such resistance embarrassed American Express when the company started greeting callers by name -- before they identified themselves. ''People didn't like it, they were startled, so we stopped doing it,'' says Maureen Bailey at American Express.

Many mail-order companies, including L.L. Bean in Freeport, Maine, use ANI to pull up information quickly on repeat customers. Some firms refuse to quote prices until the caller is registered in their database.

Although new technology makes it easier to gather information, most companies still rely heavily on consumers to volunteer information through warranty cards and surveys. ''When we quite often give information in a retail store about ourselves, we think it is in connection with the transaction that we're making, but in fact it's simply to make direct marketing a little easier,'' says Robert Ellis Smith, publisher of the Privacy Journal.

Direct marketers respond that their data lists only help consumers. ''There's nothing sinister, evil, or negative,'' says Adler of Call Processing Solutions, whose clients have included Hewlett Packard and Apple Computers. They want to ''understand more about the people who buy, use, and enjoy their product,'' he says.