This article reports on three pragmatic randomised controlled trials (RCTs) to help children at risk of conduct disorder (CD): two involved the Incredible Years (IY) BASIC parent programme and the other concerned the IY teacher programme. All three interventions took place in regular service settings in
North- and Mid-Wales. In all three studies, staff from the provider agency delivered the programme and participated in RCT evaluations in which participants were randomly allocated to intervention or waiting list control conditions. After a brief introduction to research into the prevention or treatment of CD, and the issues to be considered by services in selecting and delivering interventions, this article summarises the structure, content and evidence base of the IY programmes. The three Welsh studies are briefly
described before exploring what factors contributed to service participation in the trials and the benefits and lessons learned in undertaking them.