Epidemiological data on trigeminal unilateral autonomic symptoms in patients with migraine are scarce. The authors wanted to provide a population-based evaluation of the prevalence of unilateral autonomic features in migraine patients and an assessment of the expression of unilaterality of autonomic symptoms and head pain in patients with UAs compared to other migraine patients. A population based sample of 6000 inhabitants of the city of Essen in Germany was screened using a previously validated standard questionnaire. Three thousand three hundred and sixty subjects (56% of a total 6000) responded. 841 subjects had migraine, out of which 226 reported accompanying unilatral auetonomic symptoms (26.9%, CI 95% [23.9-30%]). Unilateral autonomic symptoms in patients with migraine are common and have been widely underestimated in the past. One out of four migraine patients regularly experiences one or more unilateral autonomic symptoms during their attack. Migraine patients with accompanying autonomic symptoms seem to experience their pain more unilateral and more severe than non-UA patients.