Introduction: Physical rapid growth in adolescence, which is not accompanied by appropriate social and cognitive development, and the higher levels of risk-taking and sensation-seeking traits in adolescence in compare with other age-groups, can increase the level of their engagement in high-risk behaviors.

Method: The aim of this research was to study the epidemiology of high-risk behaviors among Tehran teenager girls and boys in 1391 year. The research questionnaire was made according to the USA questionnaire model and the estimated Cronbach alpha coefficient was 0.81. The original sample size was 1280 adolescents which were selected from all grades of high-school girls and boys in Tehran city. After deleting the uncompleted or sketchy questionnaires, 1030 remained questionnaires were analyzed by SPSS software.

Findings: The findings shown that hookah smoking, cigarette smoking, sexual behavior, violent behavior, alcohol consumption were in ordinary the most frequent high-risk behaviors among Tehran teenagers. Besides, the mean of boy’s high-risk behavior was meaningfully more than girls and no differences were found between adolescents from different age-groups and ethnical groups.

Discussion: Different personal and social factors are involved in creation and development of high-risk behaviors in adolescent boys and girls, and reducing the range of them needs to long-term and short-term planning and needs to implementation of cultural and educational programs at micro and macro levels in different age-ranges.