© 2018 Elsevier Ltd ‘Channelopathies’, or mutations in ion channels, are long-established causes of epilepsy. Comprehensive genetic, mechanistic and clinical data for SCN1A, a voltage-gated sodium channel, has highlighted the differing contributions of neuronal sub-types in epilepsy and confirmed that genotype-phenotype relations, even for monogenic epilepsies, are strongly influenced by modifier genes and environmental factors. An emerging population of de novo mutations in voltage-gated potassium channels has defined two novel potassium channelopathies (KCNA2 and KCNC1), which may benefit from mechanistic insights from SCN1A. Meanwhile, increasing genetic evidence has strengthened the long-standing association of voltage-gated calcium channels with epilepsy. Finally, an integrative approach for the characterisation of genetic variation in NMDA receptors has created a new standard for predicting functional effects of novel epilepsy genes.