The Arg506 --> Gln coagulation factor V mutation (factor V Leiden) is the most frequent inherited abnormality of blood coagulation which predisposes to venous thromboembolism. Its association with an increased risk of arterial thrombosis is uncertain. We describe 3 members of the same family (a woman and her 2 children) who were heterozygous for the Arg506 --> Gln mutation and who presented cerebral transient ischemic attacks (TIA) at a young age. The patients (with the exception of one smoker) had no risk factors for TIA and no abnormality of the coagulation system other than the Arg506 --> Gln mutation. The observation of the mutation and TIA in 3 members of the same family may suggest the hypothesis of an association between the mutation and arterial thrombosis. This hypothesis must be interpreted with caution, due to the absence of objective instrumental findings in patients with TIA and to the high prevalence of the Arg506 --> Gln mutation in the general population.