Limitation of the vertebral column mobility and elasticity in ankylosing spondylitis results in an increased risk of fractures. Cervical spine fractures in ankylosing spondylitis (3.5 times more frequent than in the general population) are usually caused by minor traumas and traffic accidents. The most frequent mechanism underlying such fractures is that of extension. Fractures of the dens of epistropheus are reported very rarely. They lead to symptoms of massive spinal cord lesions. Two cases o f a dens of epistropheus fracture are described: one with tetraparesis and the other with the Brown-Sequard syndrome. They were very difficult to diagnose because of the fracture localisation. In both cases conservative treatment was applied with good results (a partial recovery from paresis).