This investigation determined the prevalence of essential tremor in a US population. The findings were derived from a large-scale morbidity survey conducted in a rural, biracial Mississippi county (Copiah County). Both the household and the institutionalized populations of the county were included. Results were limited to persons 40 years old or older. Prevalence ratios were higher for women than for men and were higher for whites than for blacks. Age-specific prevalence ratios generally increased with age. The overall prevalence ratio was 414.6 per 100,000 inhabitants.