We conducted this study to determine familial Mediterranean fever (FMF)-associated central nervous system involvement including demyelinating lesions, stroke, and posterior reversible leukoencephalopathy syndrome (PRES). Patients with MEFV mutations were systematically reviewed through the Medical Biology Unit database. All samples sent for mutation analysis were screened for 10 common MEFV mutations. Patients with FMF and neurologic disorders according to the clinical records were invited for reevaluation. Lumbar puncture, electroencephalography, and evoked potentials were used to determine the type of neurologic involvement in selected cases. Electrocardiography, transthoracic and/or transesophageal echocardiography, and magnetic resonance imaging and/or angiography were performed to clarify the etiology of cerebrovascular disease. Of 8864 patients in the genetic testing database, 18 with neurologic signs were assessed. The mean age of patients was 31.0 +/- 11.8 years, mean age at first FMF symptom was 12.6 +/- 5.6 years, and mean age at neurologic involvement was 25.8 +/- 12.2 years. Fifty-five percent of patients were women. A homozygote MEFV mutation was detected in 16 of 18 patients (88.8%), and a homozygote M694V mutation was found in 72.2% of patients. We found 7 FMF patients with demyelinating lesions, 7 with cerebrovascular disease, and 4 with PRES. The mean interval between first FMF sign and neurologic involvement was 13.7 +/- 8.9 years in the demyelinating group, and 23.4 +/- 10.3 years in the group with cerebrovascular disease. Mean stroke age was 28.5 +/- 16.4 years. All patients in the PRES group had hypertension. Three different neurologic conditions in FMF patients were noticeable. Demyelinating lesions and cerebrovascular disease were the most common clinical presentations. Approximately 70% of patients had the homozygote M694V mutation. Neurologic involvement is rare but serious in FMF.