Based on an in-depth literature review, ICCT Visiting Research Fellow Dr. Alex P. Schmid explores theterms ‘radicalisation’, ‘de-radicalisation’ and ‘counter-radicalisation’ and the discourses surroundingthem. Much of the literature on radicalisation focuses on Islamist extremism and jihadist terrorism. This isalso reflected in this Research Paper which explores the relationship between radicalisation, extremismand terrorism. Historically, ‘radicalism’ – contrary to ‘extremism’ – does not necessarily have negativeconnotations, nor is it a synonym for terrorism. Schmid argues that both extremism and radicalism canonly be properly assessed in relation to what is mainstream political thought in a given period. The paperfurther explores what we know well and what we know less well about radicalisation. It proposes toexplore radicalisation not only on the micro-level of ‘vulnerable individuals’ but also on the meso-level of the ‘radical milieu’ and the macro-level of ‘radicalising public opinion and political parties’. The author re-conceptualises radicalisation as a process that can occur on both sides of conflict dyads and challengesseveral widespread assumptions. The final section examines various counter-radicalisation and de-radicalisation programmes. It concludes with a series of policy recommendations