Visual auras (VAs) of 100 patients with migraine with aura were studied by questionnaire. Visual auras accompanied the patients' first headache (HA) in 39% of patients. Only 19% had VAs with every attack. Patients with VAs over the entire HA history had a high frequency (greater than 50%) of attacks with VA; patients with VA during only part of the HA history had a low frequency (less than 50%) of attacks with VA. The auras occurred exclusively prior to the HA in 57%. The free interval between the end of the VA and the start of the HA was usually (75%) shorter than 30 minutes. Most (59%) patients had VAs that lasted from 1 to 30 minutes. They started in the periphery of the visual fields in 56%. The most common phenomena described were: small bright dots (42%), flashes of light (39%), "blind spots" (32%), and "foggy vision" (27%). Fortification spectra was reported by only 20%. Although most (65%) patients had a combination of phenomena, the majority (72%) had only one uniform constellation of manifestations. There was no clear-cut relationship between side of VA and side of HA. Migraine VA is a pleomorphic and complex symptom. Many patients not qualifying for the diagnostic criteria of migraine with aura, as proposed by the International Headache Society (IHS), unequivocally present with visual phenomena that strongly suggest this diagnosis.