Migraine is not a disease but a syndrome that undoubtedly has multiple causes. Several migraine syndromes have a clear autosomal dominant pattern of inheritance, and recently, mutations have been found in two different genes in families with hemiplegic migraine. Familial aggregation and twin studies in families with other more common migraine syndromes (i.e., migraine without aura and migraine with aura) show that genetic factors are important, although the mode of inheritance is not always clear. Numerous candidate genes have been identified based on clinical features of migraine and the known functions of the different genes. Recently genome-wide scans in families with migraine without aura and migraine with aura have identified susceptibility loci for these common syndromes. However, none of the numerous studies performed to date provide convincing evidence for a gene responsible for the common varieties of migraine. (C) 2004 Prous Science. All rights reserved.