CONTEXT:The fragile X premutation has recently been reported to be associated with a neurodegenerative syndrome, chiefly characterized by intention tremor, gait ataxia, and executive cognitive deficits in men older than 50 years. Essential tremor is a frequent cause of tremor in elderly patients and in some cases is associated with impaired tandem gait and cognitive deficits. OBJECTIVE:To describe 2 fragile X carriers whose clinical presentation mimicked essential tremor. DESIGN:The 2 patients described herein underwent neurologic examinations by experienced movement disorders neurologists, magnetic resonance imaging, and fragile X gene, messenger RNA, and protein analyses. One underwent detailed neuropsychological testing. SETTING:Patients were studied at 2 large university movement disorders clinics. PATIENTS:Both patients were white men older than 50 years who had been diagnosed as having essential tremor and then found to be fragile X carriers. RESULTS:Besides disabling intention tremor, the 2 patients had impaired tandem, generalized brain atrophy, and unusual bilateral T2 middle cerebellar hyperintensities on magnetic resonance imaging. The patient who underwent neuropsychological testing had frontal executive deficits. Both patients had elevated fragile X mental retardation gene 1 messenger RNA and reduced fragile X mental retardation 1 protein levels. CONCLUSION:The fragile X carrier state may underlie the clinical findings in some older men diagnosed as having essential tremor.