Sneddon's syndrome is characterized by livedo reticularis and cerebrovascular lesions. We report the cases of women (mean age, 36.2 +/- 8.1 years) diagnosed with Sneddon's syndrome based on the presence of livedo reticularis and characteristic cerebrovascular findings. Seven of these patients had cerebral infarcts on cranial computed tomography scan. Antiphospholipid antibodies were positive in 6 of these cases. Three cases had abnormal levels of antithrombin III. Analyses of chromosome 6 revealed no abnormalities. In 3 of the cases, investigation of the pedigrees revealed autosomal dominant traits. Two cases had epilepsy, and 3 had migraine. One case with migraine also had myasthenia gravis. In addition, we detected inferior altudinal hemianopia in 2 cases, cognitive functional disorder in 3 and depression in 2. Based on these findings, the entire vascular, haematologic, neurologic, and dermatologic systems should be evaluated in patients diagnosed with Sneddon's syndrome.