Since the hepatitis B vaccine are on the market in France, until the end of 2002, 1211 observations of demyelinating disease of the central nervous system (1109 cases of which 895 multiple sclerosis) or peripheral (102 cases of which 49 Guillain Barre Syndrome), have been reported to the french network of pharmacovigilance and to the AFSSAPS. It is not possible to singularize these observations, neither from a clinical nor an epidemiological point of view. No risk factor has been detected. Only the chronology could suggest a causal relationship, the vaccine preceding the pathology in all the cases notified.