Dr. Megan A. Moreno and Dr. Dimitri Christakis of Seattle Children's Research Institute and the University of Washington said that as social networking Web sites such as MySpace grow, many have concerns about exposing teens to ill-intentioned online predators, cyber bullies and increased peer pressure.

There are also fears that university enrollment and future hiring decisions may be compromised by what adolescents post online in personal profiles such as MySpace and Facebook.

The research team collected data from 500 randomly chosen public Web profiles of 18-year-old U.S. men and women.

The study, published in Archives of Pediatric & Adolescent Medicine, found that 54 percent of the MySpace profiles contained high-risk behavior information, with 41 percent referring to substance abuse, 24 percent referring to sexual behavior and 14 percent referring to violence.