The study will be a multi-center, parallel, group, placebo control, double-blind, randomized controlled trial of lamictal as add-on maintenance treatment in pediatric outpatients (aged 10 to 17 years) diagnosed with Bipolar I disorder. The study consists of 4 phases: Screen (approximately 2 weeks), Open label phase (up to 18 weeks), Randomized phase (up to 36 weeks) and Taper and follow-up phase (up to 4 weeks).