Essential tremor (ET) is the most common adult movement disorder, as much as 20 times more prevalent than Parkinson's disease. Estimates of the crude prevalence of ET range widely from 0.08 to 220 cases per 1000 persons, a 2750-fold difference. There has been no formal attempt to synthesize these disparate results. Our purpose is to provide an overview of existing studies, to examine methodologic issues that may account for this tremendous variability in results, and to provide a more precise estimate of the prevalence of ET. Nineteen studies of the prevalence of ET were reviewed. Factors that contribute to the broad range of prevalence estimates include (a) differences in study design that influence validity and (b)

Essential tremor (ET) is a 4-to 12-Hz postural and kinetic tremor.'The severity of tremor may vary considerably, from a mild, low-amplitude, nondisabling tremor to a jerky, high-amplitude tremor that may be recalcitrant enough to warrant deep brain electrical stimulation or chemothalam~ tomy.~*~ In one clinic-based cohort, as many as 15% of individuals with ET were forced to retire early because of functional compromise related to their tremor di~ order.~