The purpose of the present research was to assess the relative influence of instigation or inhibition in mediating retaliation after arbitrary or non-arbitrary frustration. Sixty-four men were asked to learn a concept that was being taught by a peer. Although all men were frustrated, half were deliberately frustrated while the other half were not deliberately frustrated by the teacher. Following the task, the learner was given the opportunity to prevent the teacher from gaining employment under conditions where his evaluation was either anonymous or to be made public. The results of a 2 × 2 analysis of variance yielded several significant effects. The data revealed that subjects rejected the teacher more when the frustration was arbitrary than when it was non-arbitrary. Moreover, when the evaluation was anonymous, subjects rejected the teacher more than when the evaluation was to be made public. Furthermore, the difference in the amount of rejection expressed between arbitrary and non-arbitrary conditions was greater when the evaluation was anonymous than when it was public. These results were interpreted as demonstrating the greater contribution of instigatory rather than inhibitory factors in expressing aggression following deliberate or non-deliberate frustration.