The review shows the statistics about the epilepsy morbidity in different countries, including Russia and its individual regions. We discuss various mechanisms of development of epileptic hyperexcitability of brain neurons. We summarize the knowledge about the role of ion imbalance, transmitters, neurochemical disorders in the epileptic activity development, both acquired and hereditary, including the significance of molecular genetic alterations, namely mutations and epigenetic mechanisms that together cause pathological changes in the membrane potential of brain neurons. The article highlights the causes and mechanisms of development of membrane channelopathy and transmembrane ion transport disorders, which underlie changes in the electrophysiological properties of neurons. The article provides information from Russian and foreign literature about the significance of immunological and cytokine shifts in the pathogenesis of epileptic hyperexcitability of neurons in different parts of the brain.