Why do we need randomised controlled trials to assess behavioural interventions?

The value of the randomised controlled trial still generates debate. Although some of the earliest examples of these trials can be found in behavioural and psychosocial research, this is not an area that has adopted readily the randomised controlled trial to assess interventions. Two recent developments have intensified debate about the role of randomised controlled trials—the urgent need to find effective behavioural interventions against HIV 4 and the advance of evidence based medicine, which is moving the randomised controlled trial beyond clinical trials into areas such as health promotion. This article considers the merits and limitations of randomised controlled trials in the behavioural area compared with clinical medicine, and asks how these trials can be applied successfully to assess behavioural interventions.