Nine women (age 22-43 years) with cerebrovascular diseases (CVD) related to pregnancy, puerperium or contraceptive use were studied. Five were pregnant, 2 were post partum and 2 were taking oral contraceptives. All under- went a complete etiological examination including assessment for the thermolabile C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene mutation. Three of the 9 patients were homozygotic for the C677T MTHFR mutation, and 3 were heterozygotic. In these 6 patients, no other etiology could be found. Mutation in the thermolabile MTHFR gene might be an important cause for CVD related to peripartum or contraceptive use.