An association between multiple sclerosis (MS) and exposure to organic solvents has been discussed. Organic solvents are metabolised by enzyme systems like glutathione Stransferase M1 (GSTM1) and CYP2D6, which express polymorphisms in the general population. GSTM1 null genotype has been associated with solvent-induced chronic toxic encephalopathy. Our aim was to see if a defect in one of these enzyme systems could explain the association between MS and exposure to organic solvents. In our study, 50 patients with MS were investigated, including 24 who had been significantly exposed to organic solvents and 26 who were not exposed. Polymerase chain reaction-based methods were used for genotyping GSTM1 and CYP2D6 polymorphisms in leukocyte DNA. No differences in genetic predisposition were found between MS patients exposed and those not exposed to organic solvents regarding GSTM1 null or CYP2D6 poor metaboliser genotypes. The possible association between multiple sclerosis and solvents may not, as for chronic toxic encephalopathy, be explained by defects in these systems.