Intolerance to smell is often reported by migraine patients. This study evaluates osmophobia in connection with the diagnosis of migraine and episodic tension-type headache (ETTH). The characteristics of this symptom are also investigated. We recruited from our Headache Centre 1005 patients (772 female, 233 male; age 37 +/- 11 years), of whom 677 were migraine without aura (MoA), 130 migraine with aura (MA) and 198 TTH. Patients with two or more forms of primary headache were excluded. Among migraine patients, 43.9% with MoA and 38.5% with MA reported osmophobia during the attacks; none of the 198 TTH patients suffered this symptom. Most frequently offending odours were scents (63.9%), food (55.2%) and cigarette smoke (54.8%). Osmophobia appears structurally integrated into the migraine history of the patient. It seems to be a peculiar symptom favouring the diagnosis of migraine (MoA and MA) in the differential diagnosis with ETTH.