The present study aimed to evaluate the factor structure of the Reactive-Proactive Aggression Questionnaire (RPQ) with Turkish children, and to investigate gender, grade-level, and socioeconomic status (SES) differences in reactive and proactive aggression. Participants consisted of 1,081 Turkish children (544 boys and 537 girls) aged 9 to 14 years. Findings from the confirmatory factor analysis provided evidence for the two-factor reactive-proactive model. It was also found that the factor structure of the RPQ was the same across gender groups. Reactive and Proactive Aggression scales and Total Aggression scale showed high internal consistency. Boys got higher scores on both Reactive and Proactive Aggression scales. Reactive and proactive aggression increased with age until Grade 7 in both boys and girls. Finally, the findings showed that, for both boys and girls, children with low SES had significantly higher reactive and proactive aggression scores than children with middle and high SES. (Contains 3 figures and 5 tables.)