More and more people are communicating with each other online, as use of the Internet spreads. Part of this phenomenon is online dating. Recent research shows that homosexual men are especially interested meeting sex partners this way. With the HIV rate going up in the United States among homosexuals and other groups, public health officials are seeking to reach gay men where they meet - on the Internet - with advice on avoiding the virus.

The Internet is becoming the preferred way for male homosexuals to meet other like-minded men. Their use of personal ads and discussion forums, called chat rooms, is increasing rapidly. University of California HIV researcher Gregory Rebchook said gay users find the network very convenient.

"What we are hearing from the participants in terms of why they are using the Internet is that they find it amazingly easy and efficient and low cost, and that there is just a wide range of partners available to them," Mr. Rebchook said.

Recent public health surveys of homosexual men in London and of gay California men with syphilis found that more than one-third of them found partners online. In the California study, the figure had been about one-eighth just two years ago. California Department of Health Services investigator Terrence Lo said the Internet is surpassing traditional meeting places for gay men.

"The Internet is more commonly reported than bathhouses, sex clubs, or bars and clubs as a venue for meeting partners," Mr. Lo said.

But the California survey demonstrates the health dangers that Internet dating can pose, with so many of the state's male syphilis patients seeking partners online.

According to other U.S. and British studies, about one-third of gay men surveyed admitted to having unsafe sex with partners they met online - either unprotected sex, multiple partners, or both.

The trend worries public health officials like Dr. Ronald Valdiserri, who oversees HIV prevention programs for the U.S. government's disease-tracking agency, the Centers for Disease Control. "These studies add to the growing body of research that points to the Internet as an emerging risk environment for unsafe sexual behavior," he said.

This is even more worrisome in view of recent U.S. government data showing a seven percent jump in HIV diagnoses last year among homosexual men. They make up about half of all new HIV infections in the United States, and the increase in their infection rate is a big reason the overall U.S. HIV rate increased last year for the first time in nine years.

No one knows whether increased Internet contacts have played a part in the reversal. Dr. Valdiserri attributes the resurgence to treatment failure, difficulty adhering to a complicated drug regimen, late diagnoses, and a false sense of security after years of declining HIV rates. But he said, just as the Internet can facilitate unsafe sex, it can also be used to encourage healthy behavior.

"We consider this an extremely important new and evolving area of public health. We need to now get caught up and think about how maybe the Internet can be used to further prevention efforts," Dr. Valdiserri said.

Programs in San Francisco, Detroit, and Seattle are doing this. Counselors in those cities are entering Internet chat rooms, or making postings on Web sites popular with homosexuals, offering prevention information and referral to HIV testing, treatment and care. The University of California's Gregory Rebchook told a recent U.S. government HIV prevention conference that the men are receptive to online intervention.

"We found that people were actually excited to talk to us and had a lot of important things to say about HIV prevention and creating opportunities online. Nearly everyone that we talked to mentioned that they would be willing to participate in online HIV prevention efforts and felt those prevention efforts were important," Dr. Rebchook explained.

Researchers said online HIV intervention works because the format protects anonymity and makes individual exchange possible between a counselor and participant.

Dr. Ronald Valdiserri of the Centers for Disease Control says stemming the HIV epidemic requires novel strategies to reach high-risk populations.