A 12-week Evaluation Period will be used to characterize potential cognitive and neuropsychological effects of LEV (20 - 60 mg/kg/day), as adjunctive treatment in children 4 - 16 years old, inclusive, with refractory partial onset seizures when compared to adjunctive treatment with placebo.

Inclusion Criteria:

• Pediatric subjects (4 - 16 years old) diagnosed with refractory partial onset seizures for a minimum of six months prior to Visit 1 experiencing at least two partial onset seizures during the four weeks prior to Visit 1 will be enrolled
• Subjects should be on a stable regimen of one or a maximum of two other antiepileptic drugs (AEDs) for at least 2 weeks prior to Visit 1
• Subject must have an Intelligence Quotient (IQ) as assessed during Visit 1 of at least 70
• Subject and parent/guardian should be fluent in English

Exclusion Criteria:

• Subject must not have had previous treatment with levetiracetam unless, in the opinion of the investigator, the subject's previous treatment was inadequate in dose or duration to provide an accurate assessment of the therapy, or the effect of levetiracetam was confounded by concomitant medication
• Subject is receiving benzodiazepines on a routine or chronic basic and is unable to discontinue use four weeks prior to Visit 1
• Subject has seizures too close together to accurately count
• Subject has a current psychiatric disorder other than mild to moderate attention deficit, behavior, or learning disorders