Background: Little research has been conducted investigating the way in which personality constructs relate to people with intellectual disabilities. The small amount of research that does exist suggests that underlying personality structure may be considerably different to that found in mainstream research. This hypothesis is, however, untested because so little work has been conducted with this population. Method: Two circumplex models, the Interpersonal Adjective Scales and the CIRCLE, were employed to explore the factor structure, coherence and fit of these models with this population. One hundred and twenty-three participants from forensic intellectual disability services were rated by staff on the assessments, although not all assessments were completed for all participants. Results: The factor structures for both assessments conform broadly with a theoretical structure. Hypotheses concerning the magnitude and direction of Spearman's correlations both within and between assessments were generally confirmed. Conclusion: While results would support the applicability of mainstream personality assessments to this client group, cautions were expressed in relation to the source of the sample and to the method of data collection. (Contains 3 tables and 1 figure.)