To study the demographic and clinical correlates of essential tremor (ET), we analyzed a comprehensive database of 350 patients evaluated at the Movement Disorders Clinic at Baylor College of Medicine from 1982 to 1989. The age at onset of tremor showed bimodal distribution for both male and female patients, with peaks in 2nd and 6th decades. ET appeared most frequently in hands, followed by head, voice, tongue, leg, and trunk. Half of the patients (47%) had associated dystonia, including cervical dystonia, writer's cramp, spasmodic dysphonia, and cranial dystonia, and 20% of the patients had associated parkinsonism. At least one 1st-degree relative of 62.5% of ET patients reported tremor. Alcohol relieved tremor in 2/3 of ET patients. Sixty-eight percent of patients who had adequate follow-up improved with propranolol, and 72% with primidone. There was no significant difference in various clinical variables between the 219 patients with familial ET and 131 with sporadic ET. Patients with early-onset ET were more likely to have hand involvement and associated dystonia than patients with late-onset ET. Dystonia was more frequently associated with mild ET than with severe ET. Patients with low-frequency tremor were older and had more head but less hand involvement than patients with high-frequency tremor. The lack of relevant differences between ET subgroups suggests that, despite variable expression, ET represents a single disease entity.