There has been a remarkable growth of interest throughout the world in the phenomena of bullying or peer victimisation in schools (Smith, Morita, Junger-Tas, Olweus, Catalano, & Slee, 1999; Smith, Pepler, & Rigby, 2004). It has been repeatedly claimed that involvement in bully/victim problems at school, either as a bully or as a victim or as both, constitutes a significant mental health risk for children. This article examines the research evidence for this contention, drawing largely upon relevant cross-sectional survey results and retrospective and longitudinal studies, and discusses factors that may impinge on the suggested relationships.