The limited literature on awareness of differences and stigma in people with intellectual disabilities is largely sociological, emphasises pathology, and has rarely used a developmental perspective with representative samples. Interviews, photographs and standardised tests were used to investigate such awareness with 77 young adults with Down syndrome and their parents. Awareness and social categorisation were significantly associated with verbal mental age, and closely approximated the typical social-cognitive developmental sequence. No associations were found between awareness and chronological age, parent telling, gender, and mainstream experience. Only those with verbal mental ages from around 8 years were making relative social comparisons and beginning to form complex social categories of Down syndrome/disability. Around 13% were rated as showing a negative emotional reaction to Down syndrome/disability, and most of these were male. A similar percentage, mostly female and with higher verbal mental ages, discussed concerns and limitations. Even so, they all had high self-esteem and awareness of Down syndrome and disability did not appear to be a major issue. A number of coping mechanisms to maintain a positive sense of self were suggested. It is argued that both sociological and developmental models are required to inform parent and professional attempts to facilitate self-awareness.