Because of anthrax, people aren't opening strange paper mail. Because of computer viruses, they aren't opening strange e-mail.

What's a direct marketer to do?

Persuade people to pass along corporate pitches to personal friends.

It's called "viral marketing." And some direct marketers, who have seen growing use of the technique in recent years, think it's going to become an increasingly important part of marketing campaigns.

"You'll see more of it because the open rate" -- how many of the e-mail pitches are actually opened -- "is so much better," says David Kenney, chief executive of Digitas Inc., a Boston marketing firm that has run viral-marketing campaigns for such blue-chip advertisers as General Motors Corp., Johnson & Johnson and Gillette Co.

Infectious Idea

When Boston-based Gillette was introducing the three-bladed Venus razor for women last spring, one target group was college students, and Digitas designed a truck that traveled around the spring-break circuit in Florida, parking daily near a beach. The truck crew invited women to come in and get some aromatherapy, learn about Venus, enter a sweepstakes and make a digital greeting card with a picture of themselves enjoying the beach.

The viral part came when they e-mailed the cards to friends. The messages automatically included a chance to enter the sweepstakes, "Celebrate the Goddess in You," and if e-mail recipients entered the contest, they saw a pitch for the Venus razor. Mr. Lynch says some 20% of the entries came from the viral-marketing cards, significantly expanding the audience for the product beyond the beach-site promotions.

Viral marketing is designed to mimic that most-valued of all advertisements -- a word-of-mouth recommendation. Ad veterans say one of the all-time best viral marketing campaigns was MCI Corp.'s "Friends and Family" calling plan. It gave people reduced rates for calling a circle of people, who were encouraged to buy MCI long distance in turn.

Join the discussion1: What do you think of viral marketing via e-mail? Is this really a new form of word-of-mouth advertising or is it just a new form of spam? How effective is this form of marketing?

Viral marketing works because friends "are better at target marketing than any database," says Steven Lynch, creative director at Digitas. "The idea is to get your constituency to do your marketing for you." Mr. Lynch says that "the Web has transformed viral marketing" because it's easier to pass on e-mail than messages in any other medium.

But most people don't want to pitch products to their friends, even for a small payment from the advertiser. So viral campaigns are designed to woo their cooperation. Mr. Lynch says people will forward pictures, such as those used in the Gillette campaign, or they will pass along entertainment or compelling offers -- the trick is to make sure the marketing message is in the e-mail along with the goodies.

Uncertain Count

Viral e-marketing hasn't exploded yet, in part because it isn't clear how well it works. Advertisers can tell if an item is forwarded from their client's site, but they have no easy way of knowing how often that message is subsequently passed along. It's also tricky to craft campaigns that aren't so heavy-handed that people will be turned off and refuse to send them along. And sometimes campaign techniques, such as sweepstakes entries, don't get forwarded because people fear they'll reduce their own chances of winning.

Still, advertisers are warming to the idea. Annette Lloyd, director of advertising at GM's Pontiac division, says viral marketing on the Internet works well with the young crowd Pontiac wants to reach. Pontiac has been running a television campaign around the theme of taking road trips with friends and urging viewers to check out its Web site. She says that from there "somewhere between 20% to 30% actually e-mail a friend" about Pontiac's contest to win weeklong car trips and record them, with a chance that the footage will be used in new TV commercials.

Hidden Persuaders: Viral marketing offers people something they'll pass along to pals, such as pictures of themselves at the 'Venus' van, a quiz or an animated egg.

Another success story is told by London-based MiniClip Ltd., which last July built a 600,000-name mailing list of registered users after it created DancingBush -- an animation of the president boogeying to music from the movie "Saturday Night Fever." Tihan Presbie, a London futures trader who started MiniClip, estimates that at least 10 million people must have viewed the animation to get such a large number of registered users. Nearly all of them came to the Web site because friends and acquaintances sent them the animation or the address.

Mr. Presbie says MiniClip is currently working with a U.S. rap singer on a viral campaign slated for later this year. "The future is targeted marketing," he says. "If we wanted to reach women under 25 that play soccer, we could make a MiniClip of young women playing soccer, and it would be forwarded to that target group."

At its most basic, when Digitas creates a direct e-mail campaign promoting, say, a handbag sale at client Neiman-Marcus, it routinely includes a "forward to a friend" button. Presumably, women who have given their e-mail addresses to Neiman-Marcus, or who are on lists that Digitas buys for the campaign, will know other women who like Kate Spade purses.

Johnson & Johnson, based in New Brunswick, N.J., came to Digitas seeking ways to get teenage girls to check out its Clean and Clear skin-care products. Mr. Lynch says Digitas created a "microsite" from which teens could "send a talking postcard to your friend." The pop-up advertisement appeared at teen site www.bolt.com.

Easy Audio

Digitas was taking advantage of a new technology that lets users send sound without first downloading online software -- a "plug-in" program -- to make it work. The challenge of downloading and retrieving plug-ins turns off many users, Mr. Lynch says.

When users clicked onto the pop-up, they were linked to a Web site where they could design an e-greeting card, choosing decorations such as animated flowers or messages such as "Best Friends 4ever." They were offered a phone number to dictate a short voice message. When the e-mail was sent, the recipient would open the message and hear the recording through the computer's speakers. As soon as they played the message, they were invited to click on a button called "Skin analyzer." Then they would see Clean and Clear's main Web site, "where the marketing work gets done," says Mr. Lynch.

Digitas has also helped GM develop its online marketing, and as part of Pontiac's current road-trip contest, has a Web-site survey labeled "the Destinator."

Sample question: "Which sign would you get off the highway for?"

Sample answers: "Homemade pecan pie"; "Warning, hitchhikers may be prison escapees"; and "Wooden chain-saw bears $19.95."

After taking the quiz, viewers are urged to pass along their results to friends to "see if they travel well together," says Mr. Lynch.

In an effort to augment TV advertising with the Web, Digitas created an unusual addition to AT&T; Corp.'s sponsorship of the Discovery Channel's "When Dinosaurs Roamed America." During the show people were urged to check out an associated Web site. When they did, they got the opportunity to send a virtual, animated dinosaur egg to a friend. Recipients could answer paleontological questions and then see the dinosaur hatch. Then they were invited to click through to a master site, where AT&T; branding was heightened.

More than 100,000 people hatched dinosaur eggs and clicked to go to AT&T;'s Dino site, says Mr. Lynch.