The objectives of the present study were to describe the clinical characteristics of patients with severe familial non-hemiplegic migraine with aura (NHMA) and to compare these data to those from cases in previous population-based Danish studies using the same methodology. NHMA families were recruited from the Danish patient registry and from Danish neurology practices. A total of 362 NHMA patients were diagnosed according to the 1988 International Headache Society criteria using a validated semistructured physician-conducted interview. Visual aura occurred in almost every NHMA attack. In aura without headache visual aura occurred primarily in isolation. Aura without headache was most common in older, male patients. Several clinical characteristics of familial NHMA differed from migraine with aura in the general population: firstly, the age at onset was lower, secondly, the age at cessation was higher, thirdly, aura symptoms were more severe and finally, the co-occurrence of migraine without aura was higher in familial NHMA. There seems to be a correlation between more severe symptoms and familial aggregation. These results have both clinical and scientific implications.