Four percent of American youths online have been asked to send a sexually explicit photo of themselves over the Internet, researchers say in a new study.

Of the 65 youths in the study who reported receiving a request, only one actually complied. But researchers say that's still a troubling number: With millions of youths online, that projects to potentially thousands across the country.

"One of the things we really need to start doing is talk to kids more directly and informing them of the criminal implications of this type of thing, encouraging them to be aware of these situations and to report them," said Kimberly J. Mitchell, a research professor at the University of New Hampshire's Crimes Against Children Research Center.

She said youths engaging in such behavior, not just the people making the requests, are potentially violating child-pornography laws.

Mitchell said kids also may not be aware of how quickly such photos can circulate, mistakenly thinking the image is only for the personal use of the requester.

The study, based on telephone surveys of 1,500 Internet users ages 10 to 17, was being published Friday in the Journal of Adolescent Health. The survey has a margin of sampling error of plus or minus 2.5 percentage points.

Mitchell and researchers David Finkelhor and Janis Wolak are part of a team that has been analyzing data from the March-June 2005 survey, sponsored by the government-funded National Center for Missing and Exploited Children. Mitchell said the numbers might even be higher today with the availability of camera phones and other photo-capturing gadgets.

Earlier, the same researchers suggested that warning children against posting their personal information online doesn't necessarily make them safer from predators and related threats. The researchers found no evidence that sharing personal information increases the chances of online victimization, such as unwanted sexual solicitation and harassment.

In the latest study, the researchers identified certain traits as making a youth prone to receive a request for a sexual picture. They include having a close relationship with someone known only online; talking with someone online about sex or having a sexually suggestive screen name; and experiencing physical or sexual abuse offline.

Researchers also found that requests were more likely to occur when youths were with their friends.

"A lot of kids are using the Internet in groups," Mitchell said. "When they are with friends, maybe they are egging each other on to do something they wouldn't normally do."