The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage and administration of levetiracetam are reviewed. Levetiracetam is an adjunctive treatment for partial-onset epileptic seizures. This drug inhibits seizure activity via a mechanism that does not involve excitatory or inhibitory neuronal pathways. Oral bioavailability is about 100%, and food does not alter absorption. Levetiracetam is minimally plasma protein bound (10%). Peak time to absorption after oral administration is one hour, and steady state is achieved in two days with twice-daily administration. Three clinical studies have demonstrated levetiracetam's ability to reduce seizure frequency in patients with partial-onset epilepsy. The most commonly reported adverse effects in clinical trials were somnolence, dizziness, infection, and asthenia. The potential for interactions with medications that are hepatically metabolized is minimal. The starting dosage is 500 mg twice a day; the maximum dosage is 3000 mg/day within four weeks. Levetiracetam is effective as an adjunctive treatment of partial-onset epilepsy with or without secondary generalization.