Two studies investigated the psychometric properties of a self-report measure of commonly recognized forms of aggression (FOA) that could be used to efficiently gather aggression data in large samples. EFA and CFA in Study 1 suggested that a five-factor model (Physical, Property, Verbal, Relational, and Passive—Rational) best represented the data across high school and college students. However, factor analyses in Study 2 using an ethnically diverse university sample revealed a four-factor solution (combining Physical and Property items). As a confirmation of the construct validity of FOA, physical and property aggression were lower, and verbal and passive—rational aggression were higher in college versus high school students. Gender differences were observed across FOA subscales, except relational aggression. FOA subscales correlated as expected with other anger and personality scales. Overall, the data revealed adequate psychometric properties for the FOA and suggest that current category distinctions (e.g., direct—indirect) may not adequately account for different forms of aggression. Researchers may want to reevaluate these categories.