Adenosine is now recognized as an important endogenous modulator of neuronal excitability in the mammalian central nervous system. Adenosine is produced and released in the brain, where it exerts potent depressant effects on neuronal firing and synaptic transmission. Multiple adenosine receptor subtypes have been characterized using biochemical, electrophysiological, and radioligand binding techniques. Adenosine analogues have potent anticonvulsant actions in vitro and antagonize seizures in animals induced by a variety of mechanisms, including kindling. The future development of selective adenosine receptor agonists may provide new and more effective treatment for epilepsy.