In the management of epilepsy, selecting an antiepileptic drug appropriate for each individual patient requires matching the patient's clinical needs with the agent's specific pharmacologic attributes. In many situations, the final choice of an antiepileptic drug is based upon an agent's side-effect profile. Because side-effect profiles emerge gradually as the number of patients treated expands from the thousands to the hundreds of thousands, it is helpful to periodically update our perspective of side effects of antiepileptic drugs. For valproate, the frequency of side effects has been reduced by monitoring serum levels, using improved formulations, and limiting use in patients who have been identified as having a high risk for the development of a serious side effect.