A new survey says that one in five teens under age 18 are "sexting."
That is sending or receiving sexually suggestive photos either through cellphone text messages or email.
The National Center for Missing and Exploited Children found that teens are "sexting" despite knowing the dangers involved.
Of the teens surveyed, 11 percent said they have sent messages to strangers.
72 percent of the teens have profiles on social networking sites like Facebook or MySpace.
And most of the teens said that is where they are posting photos.
Many said their parents are clueless. Forty percent said they tell their parents little or nothing about what they do online.