PURPOSE: This prospective, open-label study evaluated the efficacy and safety of adjunctive levetiracetam (LEV) in Korean adults with uncontrolled partial epilepsy. METHODS: A total of 100 patients whose partial seizures were inadequately controlled on their current antiepileptic drugs were enrolled and received LEV (1000-3000 mg/day). Seizure count and adverse events (AEs) were recorded by patients. Global evaluation scale (GES) and quality of life (QOLIE-31) were also evaluated. Additionally effectiveness over 1-year follow-up was investigated. RESULTS: Ninety-two patients completed the short-term 16-week trial. The median percent reduction in weekly seizure frequency over the treatment period was 43.2%. The > or =50% and > or =75% responder rates were 45.4% and 36.1%, respectively. Seizure freedom was observed in 17 patients throughout the initial 16-week treatment period. On investigator's GES, 81 patients were considered improved, with 41 patients showing marked improvement. Most QOLIE-31 scales improved significantly. At the end of the trial, 79 chose to continue follow-up treatment with LEV. At the follow-up visit (ranging 60 to 81 weeks), 64 patients were still taking LEV; during the last 16 weeks, 65.6% of patients had > or =50% reduction, 50.0% had > or =75% reduction, and 35.9% had a 100% reduction. Seven patients showed continuous seizure freedom from the initiation of LEV treatment. During the entire treatment period, LEV was withdrawn in 36 patients; due to lack of efficacy in 22, AEs in six, both in three, other reasons in five. CONCLUSION: Adjunctive LEV therapy in patients with refractory partial epilepsy was effective and well-tolerated, as evidenced by the high seizure freedom and retention rates in both the short-term trial and the long-term follow-up.