What explains (lack of) success of behaviour change interventions? How can implementation be assessed? What are the potential and pitfalls of societal field experiments? Welcome to an open symposium tackling these issues! The 1st BeSP-symposium: Intervention evaluation & field experiments - Interdisciplinary perspectives on evaluating societal interventions to change behaviour is a high-profile multidisciplinary 2-day event around behaviour change interventions and policy. Symposium will feature international and Finnish speakers. All scholars, students and audiences interested in the behaviour change research and policy are welcome!