Background  Attitudes to the inclusion of people with intellectual disabilities (IDs) have been studied extensively, yet evidence on public awareness about ID and stigma is limited. The relationship between attitudes, knowledge and stigma associated with ID is poorly understood. The present study examined these factors and the relationships between them in the context of a multicultural society.Method  UK residents of working age (n = 1002) were presented with a diagnostically unlabelled vignette of someone with a mild ID. They were asked to label the difficulties presented and to complete measures of social distance and attitudes to the inclusion of people with IDs.Results  While attitudes to the inclusion of people with IDs were relatively positive overall, social contact was viewed with ambivalence. Inclusion attitudes and social distance were only moderately correlated. Across the whole sample 28% recognised typical symptoms of mild ID. Recognition of ID was associated with lower stigma and more positive attitudes than attribution of the difficulties presented to other causes. White Westerners showed increased knowledge, lower stigma and favoured inclusion more than participants from ethnic minorities. Among the latter group, Asians showed lower stigma and attitudes more in line with inclusion policies than participants of Black African/Caribbean backgrounds. Once a host of contextual factors were considered jointly, only contact was consistently associated with the variables measured.Conclusions  Stigma associated with ID is of concern across all ethnic groups, although it appears to be increased among the public from ethnic minorities. Given that contact and awareness are associated with reduced stigma, they should be considered as prime foci for efforts to tackle ID stigma. The current findings serve as baseline for attempts to increase public awareness and tackle stigma.