Aggression is an important risk factor for various forms of problem behaviors in adolescence, and research has often distinguished between reactive and proactive forms of aggression. The aim of the present study was to compare the psychometric properties (i.e., structural invariance, internal consistency, and criterion validity) of the Reactive–Proactive Aggression Questionnaire (RPQ) between males and females among a mixed-gender school sample of 782 Portuguese youth (M = 15.87 years, SD = 1.72). Confirmatory factor analysis revealed that a two-factor first-order structure obtained the best fit and cross-gender measurement invariance was demonstrated after excluding item 21. The Portuguese version of the RPQ demonstrated generally adequate psychometric properties of internal consistency measured by Cronbach’s alpha and omega coefficient, convergent validity, discriminant validity, criterion-related validity, and known-groups validity. Findings are discussed in terms of the use of the RPQ with male and female youths.
