Introduction. - Although multiple sclerosis (MS) and antiphospholipid syndrome (AS) are usually defined by specific criteria that make them eistinguishable, in some cases, transition between the two diseases based on clinical and brain imaging findings is not clear.Methods. - Our study included 62 patients (sex ratio F/M = 1.48; mean age 43.4 +/- 23.6 years) with diagnosis of MS according to Poser criteria and 31 control subjects (sex ratio F/M = 9.3, mean age 37 +/- 17 years). We examined the level of antibodies against phospholipids (anticardiolipid, anti beta2-glycoprotein 1 and antiphosphatidylethanolamine antibodies), antinuclear, anti native DNA, antiprothrombinase antibodies and rheumatoid factor.Results. - Antiphospholipid antibodies were found with a significant level (anticardiolipid > 30 UI, anti beta2-glycoprotein 1 positive) in only five patients (8%) with MS; two others showed an increase in antinuclear antibodies (1320 o and 11280 o .Conclusion. - In contrast with data recently reported, this study failed to find a significant level of antiphospholipid antibodies in MS. This result argues for the existence of different pathogenic mechanisms in MS and AS.Propos. - Bien que la sclerose en plaques (SEP) et le syndrome primaire des antiphospholipides soient habituellement definis selon des criteres specifiques qui permettent de les distinguer, dans certains cas la transition entre les deux maladies a partir de donnees cliniques et d'imagerie cerebrale apparait difficile.Methodes. - Nous nous sommes donc propose d'etudier les taux d'anticorps anti-phospholipides (anticorps anticardiolipides, anti-beta2 glycoproteine 1 et antiphosphatidylethanolamine), d'anticorps antinucleaire, d'anticorps anti-ADN natif, d'anticorps anti-prothrombinase et du facteur rhumatoide chez 62 patients (sex-ratio F/M = 1,48; moyenne d'age: 43,4 +/- 23,6 ans) pour lesquels le diagnostic de SEP selon les criteres de Poser a ete etabli et 31 sujets temoins normaux (sex ratio F/M = 9,3; moyenne d'age = 37 +/- 17 ans).Resultats. - La presence d'anticorps anti-phospholipides a ete trouvee a un taux significatif (IgG anticardiolipides > 20 UI, anti-beta2 glycoproteine 1 positive, anticorps antiphosphatidylethanolamine positive) chez seulement cinq patients (8%) suivis pour une SEP; des anticorps anti-nucleaire eleves (1320 e m e et 11280 e m e ) ont egalement ete mis en evidence chez deux autres d'entre eux.Conclusion. - Contrairement a certaines etudes recemment publiees, nos resultats ne retrouvent pas un lien significatif entre SEP et anticorps anti-phospholipides et vont contre les arguments d'un mecanisme etiopathogenique commun.