We review epidemiological data on primary blepharospasm (BSP). There is a large variation in the stated prevalence of BSP, with crude estimates ranging from 16 to 133 per million in different studies. A large proportion of this variability may be the result of differences in physician education on BSP. Age and female gender may increase the risk of developing BSP. The few case-control studies focusing on adult dystonias including BSP showed an increased risk in association with family history of dystonia and/or postural tremor, prior head and face trauma, and prior eye disease (e.g., blepharitis and keratoconjunctivitis), and a decreased risk associated with cigarette smoking. No association was found with age-related medical conditions such as hypertension and diabetes, family history of parkinsonism, and a history of anxiety or depression. Broocks et al. [Am J Psychiatry, 1998;155:555–557] found a significantly higher frequency of obsessive–compulsive symptoms in BSP than hemifacial spasm despite the clinical similarity. Among putative risk factors for BSP, age at onset, female gender, and prior head or face trauma may affect spread of dystonia to adjacent body regions. While limited, the body of epidemiological data support the idea that environmental and familial, possibly genetic, factors may both be important in the etiology of BSP. © 2001 Movement Disorder Society.