This study reports findings of a newly developed measure of social bullying based on Underwood's  framework of social aggression. The Social Bullying Involvement Scales (SBIS) consist of four scales measuring the extent to which children experience social victimization, engage in social bullying, witness social bullying, and intervene in social bullying. The sample consisted of 636 participants (311 females and 325 males, age range 11–16 years; 71% White). Confirmatory factor analysis supported a revised version of Underwood's framework for each of the four participant role scales. Internal consistencies for each scale ranged from .93 to .97. Results revealed that social victimization was related to an increase in anxiety, depressive, and externalizing behaviors. Social bullying was associated with an increase in general externalizing behaviors only. Social witnessing was moderately correlated with depression scores. Intervening in social bullying was not linked with psychological maladjustment or externalizing behaviors. The SBIS provides a comprehensive measure of social victimization, social bullying, social witnessing, and social intervening. Aggr. Behav. 37:177–192, 2011. © 2010 Wiley-Liss, Inc.