Background: According to WHO these is priority for finding out the educational needs of women and yong women. Therefore it is essential to studyconcerning teen girls health and puberty health. the objective of this Study is to determine the effect of group discussion as a educational method on promoting the knowldeg of teen girls concerning puberty health who live in welfare boarding centers in Tehran.

  Methods: This study is quasi-experimental study which conducted in welfare boarding centers of tehran among teen girls age 12-14 years old. Sixty and one eligible teen girls were selected for the study. To gather data a questionnaire was developed which included: Demographic information and awareness questions concerning puberty health which completed before and one month after training. Educational intervention was implemented for 3 month and the data was analysed using SPSS16 software and vilkaksun.

  Results: After educational intervention it was found that the mean of knowledge score increased frome 12/85 ± 4/7 to 22/01 ± 2/17. Findings showed that there is statistical significant (P<0/001).

  Conclusion: Group discussion as an educational intervention had a positive effect on improving the knowledge of teen girls concerning puberty health. It is concluded then that specific educational intervention can be applied related to puberty health of female adolescents.