The children with Down's syndrome are predisposed to atlantoaxial instability due to ligamentous laxity of the atlantoaxial joint. That can lead to cervical spinal cord compression. A careful neurologic examination and periodic screening for atlantoaxial instability would be very important for early detection and prompt management. We report a child with Down's syndrome who was diagnosed as atlantoaxial dislocation, long times after he showed progressive symptoms of cervical cord compression including respiratory distress.