Aggression level of high school students who have different psychological needs. This research study sought to invenstigate aggression levels high school students based on their psychological needs. Participants (n=1011) were selected from 4 high schools in Kayseri, Turkey. The level of students' psychological needs was assessed using the Basic Psychological Needs Scale, developed by Deci and Ryan (2000) and adapted to Turkish by Kesici, Bozgeyikli, Sunbul and Ure (2002). Student aggression aggression was measured using ‘the Scale of Aggression’ developed by Tuzgöl (1998). Remaining demographic information was collected through the use of a subject questionnair developed by the researchers. Data were initially analyzed through the use of a two way analysis of variance (ANOVA) and Scheffė test was used to determine the source of differences. The common effects of the independent variables (relationship need level with the spare time activities, competence need level with the educational satisfaction level originating from school, and autonomy need level and gender) were found to be significant upon the aggression points of those high school students. However the common effects of the remaining variables were not found to be significant. The basic effects of gender, perceived parental attitudes, observed family domestic violence, relationship and competence needs levels were found to be significant predictors of aggression scores for participants. Nevertheless, the main effects of having domestic violence at home, recreational activities, and autonomy need level were not found to be significantly related to the aggression level of the participants. The findings of this study were discussed in light of current related professional literature and suggestions for additional research were offered.