The purpose of this study was to determine the agressivity levels of the high school students and relation with their participation to sport activities. The sample of the study consists of totally 354 students (167 female, 187 male) which were randomly chosen  from Kadri Yörükoğlu, Plevne and Cumhuriyet High school in İstanbul. In this research, inclueding 30 question “Aggressiveness Inventory” was used to collect data which was devoloped by Ipek Ilter Kiper. The data was anaysed in SPSS for Windows 14.0 package program, by using descriptive statistic and “t” test statistical analysis methods.

Accoarding to results: from all the  students (female,male), who do sports have more assertiveness levels than who do not do sports.(p<0,05)  Although there is no difference accoarding to sexuality, the girls who participate in sport activities have more assertiveness characteristic than boys. (p<0,05) Accoarding to sexuality among the students who do not participate in sport activities,no significant difference was found.

As conclusion; participation in to sport has no effects on reducing of agresivity in high school students however it increases  assertiveness. In addition students participated in to sport  and female students are  more asssertive than non partcipated and male students.