Although short-term clinical trials provide important data regard-ing efficacy and tolerability, long-term studies are needed to address important aspects of clinical practice, such as long-term efficacy and safety. Long-term studies and post-marketing data show that the efficacy of levetiracetam is sustained over the long term and that this antiepileptic drug continues to be well tolerated, with low withdrawal rates and high retention rates. Patients continue to achieve significant reductions in seizure frequency and may achieve seizure freedom. Levetiracetam may allow patients to decrease the number of concomi-tant antiepileptic medications or withdraw to monotherapy. Add-on therapy with levetiracetam should be considered when additional control of seizures is needed.