Tardive dyskinesia remains a major concern in psychiatry. Epidemiologic data suggest that the prevalence of the disorder has increased over the past two decades. The average prevalence of TD across various populations is 15%-20%. Abnormal involuntary movements appear to be at least three times more prevalent in neuroleptic-treated patients than in patients not exposed to such drugs. The incidence of TD in a young adult (mean age 27) population is 14% after 4 years of cumulative neuroleptic exposure. The majority of these cases are mild and the condition does not appear to progress in most individuals despite continued neuroleptic exposure. Age remains the single most important risk factor for the development of TD. Recent investigations suggest that patients with affective illness may also be more vulnerable.