This is the second of three literature reviews on ideological transmission. The first review dealt with the ideological influence of the family on young people. The third review will deal with transmission by and through political and religious organisations and the media. This second review considers ideological transmission between social groups (peers), centred on educational settings, including schools, universities and university societies, and prisons. This report is structured in three parts. The first considers transmission between peers, focusing on theories explaining peer influence including social learning theory, social comparison and social identity theory. In the contexts of extremism and terrorism, researchers have drawn not only on theories of peer socialisation and influence, but on social network analysis to examine processes of recruitment, mobilisation and ideological transmission. Part two reviews selected literature on education and its role in ideological transmission. This covers both radical as well as mainstream perspectives on education as a tool for ideological instruction. This review stops short of reviewing in depth different branches of educational theory. Finally, part three considers ideological transmission in the prison estate. It includes theoretical perspectives on prison as a ‘total institution’ and those which have sought to establish greater agency for prisoners. Research on prisons has also included studies that deal specifically with extremist political beliefs of the types most closely associated with political violence, although the majority voice is sceptical of claims of widespread prison radicalisation.