Idiopathic generalised epilepsies (IGEs) affect up to 0.3% of the general population. Genetic factors play a predominant role in the aetiology of IGEs. Molecular genetic studies have mainly identified causative gene mutations in rare monogenic forms of idiopathic epilepsies. However, the genetic variants predisposing to common IGE syndromes remain elusive. Identification of recurrent microdeletions at 1q21.1, 15q11.2, 15q13.3, 16p11.2, 16p13.11 and 22q11.2 as rare but significant risk factors for IGE has provided new insights into the complex genetic predisposition of common epilepsies.