All patients seeking medical or surgical treatment for hemifacial spasm (HFS) in Oslo, Norway were identified in a service-based prevalence study. Only four hospital departments offered services for Oslo citizens with HFS. Fifty patients with HFS were treated. The total prevalence was 9.8 per 100,000. The prevalence increased with age to 39.7 among those older than 70 years. The use of antihypertensive drugs was significantly more common in HFS patients (36%) than in Oslo's general population.