Down's syndrome (trisomy 21) is the most common chromosomal aberration and is one of the major reasons for mental retardation. Down's syndrome has manifestations in many systems. The syndrome has many neurological complications, which include structural changes, mental retardation, young-onset Alzheimer's disease, strokes and basal ganglia damage. Epileptic seizures are more prevalent in Down's syndrome patients than in the general population. Cervical spinal cord instability, which is common in Down's syndrome, can cause neurological complications resulting from cervical spinal cord compression. The aim of this article is to review the neurological complications of Down's syndrome in order to increase awareness and assist doctors in diagnosis and counseling the patients' families.