BackgroundAn instrument was developed in Canada to assess impairments related to oral functioning of individuals with four years of age or older with Down syndrome (DS). The present study attempted to carry out the cross-cultural adaptation and validation of the instrument for the Brazilian Portuguese language and to test its reliability and validity.FindingsAfter translation and cross-cultural adaptation, the instrument was tested on caregivers of people with DS. Clinical examination for malocclusion was carried out in people with DS by two calibrated examiners. Inter and Intra examiner agreement was assessed by Intraclass Correlation Coefficient (ICC) and ranged from 0.92 to 0.97 respectively. Total of 157 people with DS and their caregivers were able to compose the sample. They were selected from eight institutions for people with DS in five cities of southeastern Brazil. The mean age of people with DS was 20.7 [±13.1] and for caregivers was 53.1 [±13.7]. The mean instrument score was 18.6 [±9.0]. Internal reliability ranged from 0.49 to 0.80 and external reliability ranged from 0.78 to 0.88. Construct validity was verified by significant correlations identified between malocclusion and the total instrument; and caregivers’ educational level and the instrument (p<0.05). Discriminant validity was proved as the instrument presented different mean comparing people with DS and non-DS (p<0.05).ConclusionsInitial validity tests indicated that the instrument related to the oral health for people with DS may be a valid instrument to this segment of the population in Brazil.