In an open observational study 774 patients with mostly partial epilepsy and a mean age of 42 years received an average dose of 2270 mg/day of Levetiracetam for approximately 3,3 months as add-on medication after previous treatment with standard antiepileptic drugs, most often carbomazepine and valproate, if these were either not well tolerated or did not achieve sufficient seizure control or both. After four weeks of adding Levetiracetam at a mean daily dose of 1000 mg, seizure frequency started to decrease significantly. At the end of the study, the frequency of all seizures was lowered by 50% or more in 543 patients (71%). A 75% seizure reduction was noted in 404 patients (53%), and 203 patients (38%) reported no seizures for the last 8 weeks. A total of 83 patients (10,7%) noted 123 adverse effects. In only 25 patients (3%) Levetiracetam had to be discontinued because of adverse effects. Physicians felt that the efficacy and the tolerability of Levetiracetam was very good or good in 76% and 91%, respectively. In the view of patients this was the case in 75% and 87% respectively. Moreover, 89% of patients wished to continue treatment with Levetiracetam. These results confirm - even when considering the limitations of observational nonrandomized studies - that adding Levetiracetam is of considerable clinical benefit for patients with unsuccessfully treated epilepsy.