Aim: The research sought to enhance professional understanding of the violence perpetrated by some people with an intellectual disability. Background: The violent behaviour exhibited by some people with intellectual disabilities remains poorly understood, particularly with regard to a clear and informative definition. Design: A qualitative study investigated the views and perceptions of professionals working directly with people with an intellectual disability in different settings. Methods: Twenty-two semi-structured interviews were undertaken with professionals from a variety of backgrounds, and four themes were generated through data analysis. Findings: Themes produced comprised the degree of intellectual disability, impulsivity, intentionality and unpredictability. Findings indicated tension between understanding violence as purposeful and explaining it in relation to the intellectual disability and/or additional conditions. Conclusion: Intellectual disability is central to understanding the impact of the other three themes, though there is a professional reluctance to use such knowledge as evidence to inform practice.