To facilitate the development of interventions to reduce health risk behavior among young people, we designed this study to compare risk behavior among young people and older people, to compare risk behavior profiles between young men and women, and to identify sociodemographic correlates of risk behavior among young people. Computer-assisted telephone interviews with a representative sample of 19,307 Australian men and women (response rate 73.1%) assessed alcohol consumption, cigarette smoking, injection drug use, and unprotected intercourse. Respondents aged 16 to 24 reported less healthy behavior than older people. Although men and women aged 16 to 24 had similar profiles of health risk behavior, correlates of these behaviors differed for men and women. There were few consistent sociodemographic correlates of different risk behaviors. The results suggest that young women are now as important a priority as young men for interventions. Young people remain an important target group for health promotion, with nonheterosexual young people a particular high-risk group.