The aim of this survey was to study the oral health status of Hong Kong Chinese adults with Down syndrome (DS). Sixty-five community-dwelling adults with DS (aged 17 to 42 years, 26.8+/-6.4) and age- and gender-matched controls attending a dental hospital were included in a cross-sectional survey. The subjects with DS had fewer filled (2.4+/-4.6 vs. 2.7+/-3.1, p=0.017) and fewer decayed (1.1 2.5 vs. 1.7+/-2.4, p=0.007) teeth than the control subjects. Significantly more peg-shaped maxillary lateral incisors and retained primary teeth (p<0.001) were observed in subjects with DS, compared to the control subjects. Adults who had DS had a significantly higher percentage of surfaces with detectable plaque (81.5+/-19.1 vs. 61.9+/-16.0, p<0.001) and a higher percentage of sites with bleeding on probing (76.3+/-25.8 vs. 55.6+/-21.4, p<0.001). A higher proportion of subjects with DS showed one or more occurrences where probing pocket depth was > or =6mm than control subjects (49% vs. 24.5%, p<0.021). In conclusion, while having fewer caries, Hong Kong Chinese adults with DS had poorer periodontal health than age- and gender-matched control subjects.