The study identified ostracism as a probable cause of some bullying that occurs in school groups. Two stages of ostracism were found. The first stage consists of punitive behaviors by group members that aim to change an individual's nonconforming behavior. This may include temporary exclusion from interaction with group members, which carries the threat of permanent exclusion from the group. If the individual changes his/her targeted behavior as a result of the temporary ostracism, the punitive ostracism will stop. The second stage of ostracism is permanent exclusion from the group if the nonconforming behavior persists. The threat of permanent exclusion from the group is so aversive that it often results in behavioral change dictated by group norms. A child may be ostracized for a wide range of behaviors deemed unacceptable by the group, even though the behaviors may pose no threat to the stability or safety of the group. Ostracism may escalate to more extreme forms of bullying, such as physical attacks; and when experienced over a long period can result in problematic emotional disorders. Interventions might teach children to be more tolerant of diversity and/or be more selective in targeting for ostracism only those behaviors that violate core norms that threaten healthy social activity. Ostracism experienced as bullying was examined in the experiences of 35 adults who were deaf. Semistructured interviews focused on their experiences in friendships and bullying at school, the effects of any bullying they had experienced, and how they felt bullying might be managed. 1 figure, 2 tables, and 21 references