The branched chain fatty acid, valproate, has a number of distinct pharmacological effects on the central nervous system. In experimental animals it showed clear anticonvulsant activity, an observation which led to its major clinical use as an antiepileptic agent, especially in petit mal seizures. More recently, valproate has shown its usefulness in treating mood disorders and migraine headaches. The basis for its clinical efficacy might be related to its ability to enhance central GABAergic neurotransmission or perhaps to its inhibition of Na+ channels. Whether each of the distinct therapeutic effects of valproate has the same molecular basis is not known.