SUMMARY. This report describes a patient whose clinical and radiological features confirm to those of ankylosing hyperostosis. Posterior bridging osteophytes were also apparent and these have not been previously described in ankylosing hyperostosis. We have considered alternative explanations for this finding and concluded that they were manifestations of the hyperostotic process. This unusual feature occuring in the presence of a comparatively narrow spinal canal resulted in cord compression and a spastic tetraparesis and we would therefore suggest that ankylosing hyperostosis may sometimes have serious neurological consequences.