This study will assess the efficacy and safety of BGG492 as adjunctive treatment in patients with partial onset seizures.

Inclusion Criteria:

• Outpatients ≥ 50 kg (110 lb) of weight.
• A diagnosis of epilepsy (≥ 2 years prior to screening) with partial seizures with or without secondarily generalized seizures.
• Uncontrolled partial seizures despite having been treated with at least two different antiepileptic drugs (AEDs) within the last 2 years prior to screening.
• At least 4 partial seizures during the 4-week baseline period and at least 4 partial seizures during the 4 weeks prior to the baseline period.
• Cohort 1 patients must be receiving stable treatment with 1 or a maximum of 2 AEDs.Cohort 2 patients must be receiving stable treatment with 1, 2, or 3 AEDs.

Exclusion Criteria:

• Presence of only non-motor simple partial seizures.
• History of psychogenic seizures.
• Absences, myoclonic seizures e.g. in the context of primary generalized epilepsy.
• Previous history of Lennox-Gastaut syndrome.
• Status epilepticus or seizure clusters, according to the judgement of the investigator, occurring within 52 weeks prior to randomization.
• Pregnant or nursing (lactating) women.

Other protocol-defined inclusion/exclusion criteria may apply