HERE was a time when e-mail was hailed as the killer app of the Internet, the medium that would change the way people communicate. E-mail would not simply liberate the world from telephone tag; it would flatten hierarchies, embolden the socially challenged, reshape human interaction.

But that was before spammers hijacked the world's In boxes. Now most e-mail users are inundated with unsolicited electronic junk mail; were future anthropologists to look through them, they might conclude that this was a civilization obsessed with reproductive anatomy, mortgage rates and prescription drugs.

For many people, spam is more than a mundane annoyance. It is a pestilence changing their online experience, and decidedly not for the better.

According to a report to be released today by the Pew Internet and American Life Project, a nonprofit research organization in Washington, 70 percent of e-mail users say that spam had made being online annoying or unpleasant.

One-third of e-mail users worry that spam is hindering legitimate communication because e-mail from co-workers, friends and relatives is getting lost, according to the report, based on a June telephone survey of 2,200 adults nationwide, of whom 1,300 use e-mail. Half of e-mail users said that spam had made them less trusting of e-mail in general. And surprisingly, perhaps, given what electronic communication was supposed to become, one-quarter said they had reduced their use of e-mail because of spam.

"The ever-increasing flood of spam is causing consumers to turn away from e-mail as a means of communication," said John Breyault, a research associate at the Telecommunications Research and Action Center, a nonprofit group in Washington that supplemented the Pew survey with some 4,000 anecdotes it had gathered at its Web site (www.banthespam.org) from frustrated e-mail users. "Many people we hear from are contemplating getting off the Internet altogether."

Daleena Garrelts has not abandoned the Web, but she has curtailed her use of e-mail. These days, Ms. Garrelts, 32, a human resources representative at a software firm in Cupertino, Calif., is far more willing to give out her cellphone number than her e-mail address.

"Two years ago, it would have been quite the opposite," she said in an interview. "I really discourage people from sending me general e-mail these days." If Ms. Garrelts needs to communicate with someone, she is more likely than before to pick up the telephone.

Other people, unwilling to reduce their use of e-mail but frustrated by the seeming inability of government, industry or anyone else to do much about spam, are taking matters into their own hands. They are vigilantes fighting a personal war: filtering e-mail, reporting each piece of spam they receive, changing their addresses or setting up temporary, disposable e-mail accounts to stay one step ahead of spammers. Combined with the thankless task of deleting one piece of junk mail after another, the result is a lot of time and effort spent coping with spam.

Yet according to the Pew study, many e-mail users (some 93 percent of adult American Internet users, or about 117 million people, use e-mail) feel trapped in a world of their own making. Many people have become so reliant on e-mail that they are not willing to change their address and start from scratch, for fear of missing the occasional important message.

"This translates into an issue of reliability," said Deborah Fallows, a senior research fellow at the Pew Internet and American Life Project and the author of the 33-page report, "Spam: How It Is Hurting E-Mail and Degrading Life on the Internet," that accompanies the survey.

"They worry that incoming important e-mail will get blocked by their filters or just plain lost in the morass and clutter of spam that gets into their In boxes," Dr. Fallows said.

In the Pew survey, which has a margin of sampling error of 3 percentage points and will be available at www.pewinternet.org, pornographic content topped all other categories of unwanted messages as the most bothersome, with three-quarters of the survey sample, especially women and parents, saying they were bothered by offensive or obscene e-mail. Some said it made their experience on the Internet miserable, according to the study.

Kathleen Bullington, a retired educational grant director in Des Moines, used to let her two grandchildren use her computer when they came to visit. But now, because of Mrs. Bullington's concern about pornographic spam, she does not allow them near it. In fact, unless she is hovering over them, watching every click of the mouse, the machine is off limits.

She is so exasperated that she forwards every piece of spam she receives to the Federal Trade Commission and to the authorities at America Online. She does this even though she suspects that her diligence will have little effect.

Mrs. Bullington thought about changing her e-mail address, but she worries that people she wants to hear from will be unable to reach her if they do not know she has switched addresses. "If you change your e-mail address, you cut off your right arm, so to speak," she said.

For those who are caught in such a bind - unwilling to change the address but also reluctant to give it out when it is required for, say, online purchases - several Web sites have sprung up offering disposable e-mail addresses. For a small fee, a user has the option of turning off the disposable address when it is no longer needed or becomes inundated with spam. Spamex.com, Spamgourmet.com and Sneakemail.com are just a few of the disposable e-mail generators.

Ms. Garrelts said that in addition to restricting how often she gives out her e-mail address, she spends a lot of time "trying to backtrack and get off lists" in the hope of preventing spammers from getting her address. But in doing so, she said, she knows she runs the risk of getting on more lists. The obvious solution, she said, was simply to use e-mail less.

Marc Perdue, 45, a systems administrator at the University of Virginia in Charlottesville, has decided to cancel the e-mail account of his 12-year-old daughter, Kathryn, and start over again.

For Mr. Perdue, the final straw was when Kathryn recently typed the keyword "pussycat" into a search engine while searching for pictures of animals. The results she got were not what she expected. After she unwittingly pointed her browser to one of the links, she began receiving as many as 100 pieces of e-mail a week, with subject lines like "Leather, baby" or "Grandma's giving pleasure."

While Mr. Perdue does not know how (or if) the inadvertent Web visit led to the spam deluge, he concluded, "We can probably eliminate 90 percent of this by getting rid of her e-mail account and getting a new one." He said he tried to install a spam filtering program - as 37 percent of those in the Pew survey with personal e-mail accounts have done - but found that it created more problems by blocking access to a good deal of legitimate e-mail.

"I have not come up with a really good bulletproof method of preventing that stuff," Mr. Perdue said. "I can only kill the animal after it's come into the house. I can't close the door and keep it out."

Ted Schell, 59, of Manhattan, has devised a low-tech way to keep at least some spam at bay. Mr. Schell, until recently a general partner with Apax Partners, a private equity firm, now has two different business cards, one with his e-mail address and one without. Operating on the assumption that the more he puts his address out into the world, the more likely he is to receive spam, he hands out cards with his e-mail address only to certain people.

All others just get his phone number. "If people wanted to get a hold of me, they could call and I could deal with it when I really had time to do it," he said.

Dr. Fallows of Pew said, "I think what you're seeing in all these user attempts to work around spam is their own way to preserve and save e-mail because they value it so highly."

Vivian Ong of Auckland, New Zealand, who runs an online business selling computer hardware, has gone beyond working around spam. After spending too much time each day deleting junk e-mail, Ms. Ong, 22, said, she decided to fight back, "in what little way I could." She now devotes a few minutes each day to trying to stop spammers.

"Of course, this means clicking on the links in the spam e-mails," she said. But she is willing to risk still more bombardment in order to find the offenders.

Ms. Ong usually clicks through to the spammer's Web site, finds the domain the site appears to be associated with, then digs deeper to find the actual site that the domain is registered to. "Heaps of times, the host of the spam or porn Web site is not aware of the person spamming from their hosting services, and when made aware of the person violating their terms of service they usually close down the Web site relatively soon," Ms. Ong said. "No one wants to be associated with spam."

Bob Held, 46, who lives in suburban Minneapolis, has taken to using fake names. His favorite nom de Web is Roberto Heldo. Whenever a Web site asks him to give his e-mail address in exchange for something, like downloading a free browser plug-in, he punches in an alias. The aliases, he says, are a foolproof method for tracking who is misusing his e-mail address.

On several occasions, Mr. Held has confirmed his suspicions that his e-mail address and other personal information are being appropriated by third parties without his permission. Indeed, because he has occasionally included his real street address when registering online, he once received a month's free newspaper subscription sent to Roberto Heldo, and has found a letter for Mr. Heldo in his mailbox.

Despite his best efforts, his problems with spam persist. Each morning, he checks the e-mail account he shares with his wife and three teenagers and invariably spends a few minutes purging spam.

After he noticed numerous pieces of pornographic e-mail clogging the family's In box, Mr. Held began a sleuthing operation into his children's Internet surfing habits. He was relieved to see that the lewd messages were just another symptom of an onslaught of spam and not a result of his children's Web travels.

Although filters on the computers have helped, Mr. Held remains frustrated by the spam he gets on his Web-enabled cellular phone, since sifting through and deleting unwanted messages costs him precious airtime.

Ms. Garrelts is in much the same boat. She has discovered that she can run but she cannot hide from the spammers. Now she is receiving spam on her cellphone, text messages offering prescription drugs and long-distance phone service.

"You hear the phone in the middle of the night and get up to check it because you're concerned," she said. "And it's just spam."

Michael Falcone contributed reporting for this article.