This is an open-label study evaluating the efficacy and safety of lamotrigine (LTG) for the treatment of newly-diagnosed typical absence seizures. Subjects will be children and adolescents < 13 years of age. It will be conducted at multiple sites in the US. The study will consist of 4 phases: Screen Phase (up to 1 week), Baseline Phase (24 hours), Escalation Phase (up to 20 weeks) and Maintenance Phase (12 weeks). Subjects will receive increasing doses of LTG according to the dosing schedule until attaining seizure freedom as confirmed by hyperventilation (HV) for clinical signs and a 1-hr EEG at 2 consecutive weekly visits. At that point, subjects will move into the 12-week Maintenance Phase. Subjects who do not achieve seizure freedom upon reaching the maximum dose (10.2mg/kg/day) with the specified dose escalation will be discontinued from the study. During the Maintenance Phase, the investigators will use their best effort to maintain the subjects at the efficacious dose reached. If the subjects have unacceptable side effects or inadequate seizure control, the doses of study drug can be increased or decreased as specified in the dosing schedule. Safety will be assessed by monitoring adverse events, laboratory assessments, and serum lamotrigine levels. Health outcomes assessments will also be conducted.

Inclusion criteria:

• Newly-diagnosed with absence epilepsy and never been treated with Anti-epileptic drugs (AEDs).
• Diagnosis demonstrated on one of two 5-minute hyperventilation tests.
• Investigator must judge that the subject and parent/guardian are likely to comply with all study procedures.
• Parent/guardian must given written informed consent. Subjects who are intellectually able to understand the concepts and procedures of the protocol must give assent by also signing the consent or by signing a separate assent form.
• Results of all screen assessments are judged to be clinically acceptable to the investigator and do not indicate any reasons why entry into the study would be contraindicated.

Exclusion criteria:

• Seizures are the result of a currently active, known, and identifiable intracerebral lesion.
• Has partial or generalized tonic-clonic seizures.
• Has a progressive neurological disorder defined as being unstable for at least 12 weeks prior to the Screen Phase.
• Has a psychiatric disorder requiring medication, or has had a past psychiatric condition that was both judged to be severe and required hospitalization.
• Has any clinically significant chronic cardiac, renal, or hepatic medical condition.
• Has a condition that affects the absorption, distribution, metabolism, or excretion of drugs.
• Is currently taking any psychoactive drugs to treat hyperactivity disorder or attention deficit disorder.
• Has taken any investigational drug within 12 weeks prior to the Screen Phase.
• Is sexually active.
• Is either pregnant (i.e., confirmed by pregnancy test at Screen) or breastfeeding.
• Has a clinically significant chronic medical disorder which the investigator and/or GSK medical monitor determine warrants exclusion.