A 56-year old man was hospitalized for spasmodic paraparesis with sphincter disorders. After exclusion of spinal cord compression and all other inflammatory, infectious or neoplastic causes, the possibility of a connexion with an hepatitis B vaccination performed with a recumbent vaccine three weeks before the neurological disorders appeared was considered. The pathogenesis of such a myelitis remains uncertain. It is based on the possible reactivation of a dormant virus or a crossed antigenic reaction between a protein of the vaccine and the nervous system. The course of the disease is usually favourable. The frequency of this complication would be more accurately determined if all neurological manifestations occurring after hepatitis B vaccination were reported.