OBJECTIVES: Objective of this study was to describe orthodontic findings in adults with Down's syndrome, a matter insufficiently regarded in literature. MATERIALS AND METHODS: A group of 104 adults (33.8 ± 15 years) with trisomy 21 had an orthodontic check-up in their accustomed environment. Anamnestic and dental findings completed the examination and descriptive analysis was performed using SPSS23. Relative frequencies with 95% confidence intervals were compared to the average population (SHIP-study, 2003; DMS IV, 2006). RESULTS: Among the participants 46.2% (36.3-56.2%) (SHIP 36.7%) had already undergone orthodontic treatment. In 87.5% (79.6-93%) of the patients, less than 25.6 properly functioning permanent teeth (DMS IV's mean) were found. Gingival bleeding and recessions, as well as periodontal disease, were increasingly found in older affected persons. Patients with Down's syndrome showed less crowding, e.g., maxillary incisors 28% (19.3-39%) versus 41.9% (SHIP). Frontal open bite (35.2% (25.3-46.1%) versus 3.6% (SHIP)) and frontal crossbite (40.9% (30.5-51.9%) versus 4.2% (SHIP)) were more often observed. No considerable differences in frequencies of orthodontic findings were detected in the comparison of the subgroups "18-28 years" versus ">28 years", "with" versus "without orthodontic treatment", "male" versus "female", "with" versus "without periodontal problems", or "with" versus "without orofacial disturbances". CONCLUSIONS: Within the bounds of this study, we gathered orthodontic findings in adults with trisomy 21 for the first time. In comparison to the average population, the subject group showed a greater number of complex orthodontic findings. CLINICAL RELEVANCE: These persisting dental and orofacial problems must be considered when treating patients with Down's syndrome.