In this introduction, the definition of cyberbullying will be discussed, instruments to measure cyberbullying will be described, and the state of the art of research on cyberbullying will presented. To date, most studies of cyberbullying investigate demographic factors such as the prevalence of bullying and being victimized, gender, age, and negative outcomes. Some studies investigate responses to cyberbullying, but most of them are limited to technological solutions and informing adults. Hardly any attention is paid to the underlying social psychological mechanisms in relation to antisocial behaviour in online communities and to the role of peer groups. Moreover, most studies are cross-sectional self-reports. The present special issue aims to fill these gaps by presenting studies which are focused on alternative topics using alternative methodologies. Copyright © 2012 John Wiley & Sons, Ltd.