The study presented here is the first detailed nosographic analysis of migraine aura, diagnosed using the criteria of the International Headache Society, in a sufficiently large sample for statistical analysis. Of 4,000 people, 163 had migraine with aura. Sixty-two had attacks of migraine aura with headache as well as migraine aura without headache, and seven had exclusively migraine aura without headache. Visual symptoms were most frequent (99%), followed by sensory (31%), aphasic (18%) and motor (6%) symptoms. Those with several types of aura symptoms had visual aura in virtually every attack, while sensory, motor and aphasic aura were present only in a small number of their attacks. The typical visual aura starts as a flickering, uncoloured, zig-zag line in the centre of the visual field and affect the central vision. It gradually progresses towards the periphery of one hemifield and often leaves a scotoma. The typical sensory aura is unilateral, starts in the hand, progresses towards the arm and then affects the face and tongue. The typical motor aura is half-sided and affects the hand and arm. The visual, sensory and aphasic auras rarely lasted > 1 h, while the motor aura did in 67% (six out of nine). Four people had exclusively acute onset visual aura. The duration of the aura and the characteristics of the ensuing headache were typical for migraine with aura, suggesting that acute onset aura is a real phenomenon. Headache followed the aura in 93%, headache and aura occurred simultaneously in 4% and aura followed headache in 3%. The characteristic spread of each symptom and the sequence of different symptoms suggest that cortical spreading depression is the mechanism underlying the migraine aura. Our results do not suggest that alterations of the diagnostic criteria of the International Headache Society are needed. The intra-individual variation of aura symptoms shown in this study indicates that a simplification of the International Classification of Diseases, Neurological Adaptation is appropriate.