Purpose of Review To summarise findings about the prevalence and correlates of challenging behaviour in adults with intellectual disabilities from robust research. We also describe findings on the interplay between challenging behaviour and mental health. Recent Findings Recent studies that have utilised psychometrically evaluated tools, with clear operational definitions, show similar findings on the prevalence of challenging behaviour of about 1 in every 5-6 adults known to services. We describe common correlates identified such as communication impairments, severity of intellectual disability, and living in institutional settings or congregate care. We also describe the complex and multifaceted relationship between challenging behaviour and mental health. Summary Based on recent studies, we propose a revised framework model to help understand challenging behaviour. We propose a number of areas where more research is required, particularly the development of risk tools clinicians can utilise in practice. Keywords Intellectual disability. Challenging behaviour. Prevalence. Correlates. Risk factors. Mental health This article is part of the Topical Collection on Intellectual Disabilities