Summary Introduction:?The Down's Syndrome (DS) is a genetic syndrome characterized by several changes and the Atlanto-axial Instability is critical for the otorhinolaryngologist. Objective:?Check the prevalence of atlanto-axial instability in patients with Down's Syndrome who undergo service follow-up in the Clinical Hospital of the UFPR [Federal University of Paran?] and review the need to carry out routine cervical radiography in the patients with prescription to otorhinolaryngologic surgery. Method:?Prospective study of patients with the syndrome who undergo CH/UFPR's follow up, through questionnaire and cervical X-ray. Results:?No case of IAA was found in the population studied. Discussion: we consider there's a high frequency of AAI in patients with DS, and for all patients who will take part in sports activities that involve motion of the region, or who are submitted to surgeries, an investigation with clinical and radiological exam is recommended. However, as the incidence has many variable findings we question the real validity of this research for all patients, even the asymptomatic ones. Conclusion:?In spite of a DS's peculiar change, there are no evidences of the need to research the AAI as a routine in asymptomatic patients and the symptomatology should guide the investigation. But more studies are required to evaluate the importance of the radiological exams in such cases.