A double-blind, randomized, multicenter, placebo controlled 5 parallel groups, confirmatory trial to evaluated the efficacy and safety of levetiracetam used as adjunctive treatment in patients from 16 to 65 years with epilepsy suffering from partial onset seizures.

Inclusion Criteria:

Epileptic patients who fulfill the following criteria are eligible for inclusion in the study:

• Subjects aged from 16 to 65 years at the acquisition of informed consent to the trial participation
• Seizure type: subjects with epileptic seizures which were diagnosed as partial seizures more than 2 years ago according to "Clinical and electroencephalographic classification of epileptic seizures (1981)" defined by the International League Against Epilepsy (ILAE) and confirmed with an EEG that has been performed within 1 year before Screening or at the Screening Visit
• Subjects whose previous therapy before screening involved at least two standard anti-epileptic drugs (AEDs) for partial seizures, and in whom it can be confirmed that the doses met the daily dose specified for the treatment of epilepsy in the package insert and that the therapy has been continued for at least 3 months
• Frequency of epileptic seizures: subjects experiencing partial seizures at least 12 times in 12 weeks during the Baseline Period (Week -12 to Week 0) and at least twice in every 4 weeks

Exclusion Criteria:

The following patients are not eligible for inclusion into the study:

• Subjects who were diagnosed with status epilepticus within 3 months before screening
• Subjects with no partial seizures of which frequency was measured during the Baseline Period
• Subjects who underwent surgery for epilepsy within 2 years before Screening or who were scheduled to undergo brain surgery during the study period and within 4 weeks after the completion of this study
• Subjects with a history of oral treatment with Levetiracetam (LEV)