Online support groups are internet-based networks that allow users to support each other by sharing information, advice and common experiences. In order to gain an understanding of best practice in this field, this research briefing reviews relevant research and latest practice. As such, it may be used to inform discussions about online group support alongside the findings of organisations offering such support like People Know How. The briefing looks at some technical aspects of support groups and their management, and how they may be used in different interventions. It begins with a brief history of internet-based groups and continue with an overview of some of the choices for implementing and managing online support. Then, it looks at its use in mental health interventions and discuss its use in some other areas of interest, concluding with a summary of observations.