Background: Variations in reported prevalence of challenging behaviour indicate the need for further epidemiological research to support accurate planning of future service provision. Methods: All services providing for people with learning disabilities across seven unitary authorities, with a total population of 1.2 million, were screened to identify people with challenging behaviour. Interviews were conducted with primary carers to gain data on identified individuals' characteristics and support. Measures designed for a similar study conducted in Manchester University were incorporated to allow direct comparison with earlier findings, together with standardized tools to assess adaptive behaviour and social impairment. Results: In total, 4.5 (2.5-7.5) people per 10 000 population were rated as seriously challenging, representing 10% (5.5-16.8%) of the learning disability population; the most prevalent general form was other difficult/disruptive behaviour, with non-compliance being the most prevalent topography. The majority showed multiple behaviours and multiple topographies within each general behaviour category. Also identified were substantial numbers of additional people reported as presenting challenging behaviours at lower degrees of severity. Conclusions: Prevalence rates for seriously challenging behaviours were comparable to those reported in the earlier studies, thus confirming previous findings. The prevalence of less serious challenging behaviour also has major clinical significance and emphasizes the need for enhanced understanding and skills among personnel within primary- and secondary-tier health, education and social care services, and for strengthening the capacity of community teams to provide behavioural expertise.