Media commentators have suggested that recent school shootings were precipitated by social rejection, but no empirical research has examined this claim. Case studies were conducted of 15 school shootings between 1995 and 2001 to examine the possible role of social rejection in school violence. Acute or chronic rejection—in the form of ostracism, bullying, and/or romantic rejection—was present in all but two of the incidents. In addition, the shooters tended to be characterized by one or more of three other risk factors—an interest in firearms or bombs, a fascination with death or Satanism, or psychological problems involving depression, impulse control, or sadistic tendencies. Implications for understanding and preventing school violence are discussed. Aggr. Behav. 29:202–214, 2003. © 2003 Wiley-Liss, Inc.